Amateur Astronomy Video 4 - Eyepieces, Focal Length, Magnification
HTML-код
- Опубликовано: 4 июл 2024
- This is my 4th video in my series about Dobsonian Mount telescopes. It is all about understanding eyepieces and their relation to the telescope. Learn how to determine the magnification of an eyepiece with your telescope and how to choose new eyepieces.
Наука
This is probably the single best video that I have seen explaining focal lengths and what such. Great job!!
Great video ☺👍:)
This video was extremely helpful. It made a somewhat difficult topic seem concise and easy. Keep up the great work!
You have an excellent ability to communicate concepts clearly! I’m a fan!
'Strive not be a success, but rather to be of value". Brilliant job, thanks for sharing that knowledge!
What a helpful video!! I understood quickly with you what I've read multiple times over and haven't understood. Thanks for your contribution and passion.
Dude, seriously thanks. I don't know what it is about telescope videos, but most of them are waaay too simple or way to complicated. Your the first person ive found who discussed focal length in the eye peices. Good understandable discussion!
Thanks for the feedback. Really glad it was helpful!
I'm so glad you made this video. Well done. I spent the day remembering John Dobson. Some days I really miss him.
Me Poole! Great video. It’s so much more helpful to hear videos from someone that is knowledgeable, yet Not an expert and close to the same level in the hobby as you are. Just pushed the order button on my two baaders and the fine tuning rings. Thanks for helping me decide. Oh by the way, Subscribed!
Everything I needed to know in one short video, I have got my 10 inch skywatcher out of the shed after some years will use your vids to get back into astronomy again thanks.
Great Explanation Benjamin In Layman Terms, Thank you.
Dude.... SUUUUUPER helpful. Thank you!
Your series made my life so much easier. Probably saved me some money too as i had no idea what filters and eye pieces i would need.
Bought myself a 2x Barlow, a 4mm eye piece and a natural density filter after watching the video.
Glad to hear!!
Brilliant series of videos. Can’t wait for my new Dobsonian to arrive!
Enjoy it!
Thanks for this upload, this took a lot of the mystery out of eyepieces and magnification! One thing that you could mention next time is loss of light when the different lenses are used. The more its bent, the more loss!
I cannot believe how comprehensive you were, with such a terse video. Nice video.
great video, well explain and in a very simple way that anyone can understand , THANKS for taking the time to make it
This was a great explained, thanks!
Lay my last. His explanation of the focal point made sense and I removed the Barlow. Thanks from a noob.
Great average guy delivery, nicely done. One thing I would add as a dobsonian owner like you is that field of view is much more important for us when we're pushing our telescope around but less so to somebody that has a motorized telescope, additionally the field of views are even more important as the magnification increases for a dobsonian as well as eye relief becouse it decreases on the higher magnification eyepieces. Basically that means that if you're going for super high magnifications the eye relief will decrease and field of view becomes even more important on our dobsonians. In short long eye relief and high true field of view are very important at higher magnifications but enjoyable at any magnification. For reference my telescope is a 10 inch F 4.7 1200 mm focal length and my piece collection is explore scientific 82° 24 mm 18 mm 14 mm 8.8 mm 6.7 mm and 4.7 mm. My strategy is to step down until I have a proper frame for my subject on both deep space objects and planetary. Having eyepieces all from the same series helps when they're para focal so that I don't have to change Focus when changing eyepieces.
I would like to have that 30 mm 100 degree but the exit pupil might be wasted on my older eyes now 24 mm gives a 5 mm exit pupil on my scope
Awesome videos, thanks!!
Baader Hyperion is made in China. Baader didn't even design them they just put their extension ring and camera thread modifications on an existing Chinese eyepiece, the Orion stratus, which in itself is a Chinese copy of the Japanese vixen LVW eyepieces.
Not much of baader product is actually made in Germany, similar to German behringer audio products which are also mass produced in China.
Also mixing up superview and super plossl. Super plossl was meade's trademark for the improved 5 element plossl (not really a plossl) which eventually was replaced by a standard 4 element plossl design but they kept the super plossl name. Other companies followed suit and erroneously started calling their plossls super plossls, in some cases calling stripped down versions of the plossl with minimal coatings and in some cases the lack of rubber grip rings, as plossl and calling their fully multocoated plossls with rubber grips, super plossls.
Superview is GSO's trade name for a modern erfle super wide 5 element (4 in 15mm) eyepiece.
Both the Hyperion and the explore share the common nagler design using a built in Barlow lens, effectively making the focal ratio of the scope slower which helps sharpen up the edges.
The nagler design inspired many that came after it including the radian, ethos, delite and delos from televue, the LV and LVW from vixen, and XF XL and XW Pentax eyepieces, as well as all the clones and copies that have followed such as the Meade UWA, celestron axiom LX/luminos, explore 82 and 100, even the Meade hd60 and celestron xcel and excel LX, Ultima LX, Ultima Duo, Orion epic and stratus and many others all share the nagler Smyth/negative/Barlow lens group as part of their design.
As you might be aware your hyperions can be used without the 1.25 Barlow lens part as 2" erfle type eyepieces with much worse edge performance. The spacer rings just take into consideration of a key part of Barlow lens design, its distance from the main group affects its magnification value. The farther it is the higher the increase.
You also have a 1.5x barlow, take the lens part off the Barlow and thread it directly to the nose of an eyepiece and it works at approximately 1.5x so now you can fill in gaps you might have not already been able to.
Also, the nagler effect with a GSO shorty Barlow lens threaded directly to the 15mm superview happens to make it a 10mm 65deg eyepiece that is actually sharp to the edge in your f5 dob. Some thing a superview cannot do on its own. This applies to most widefields but it is especially perfect on the 15mm
I discovered this by accident almost 15 years ago while working at OPT, when I had a "date" after work, my 10" dob lived in my car and I had forgotten my eyepieces so I had to borrow our demos (I lived 50 miles away). Knowing about the 1.5x trick I tried it on the SV15 and was pleasantly surprised.
The 15mm is the best in the superview line and was ultimately the only one I kept from that line. The 30 is decent too.
Thank you for this video!
Thank you so much! This was super helpful :)
Thank you for the video. Very helpful.
I followed your advice and got 2 baader hyperion eyepieces and with my 7mm William optics eyepiece and a 2 element 2x Barlow saw júpíter in full color for the first time.
That's great to great Gunnar!
Good stuff. Just picked up a telescope and you've helped demistify some of the topics
D J which one did you get
That gso Barlow is absolutely fantastic.it is a must
Great explanation. Thanks. 👍
Very helpful video. thanks a ton !!
Thanks brilliant.
Regards from North Wales UK
Excellent video Benjamin what eyepiece would you recommend for The Milky Way I am new to Astronomy
Great video and very informative. What I was searching for about focal lengths is extensions added to the focuser? I’m a newbie for the most part. Had a small scope as a gift and dove in and bought a Explore Scientific 16 Dobsonian used. Bought some good eyepieces. I found I had a hard time focusing as there were two extensions added to the focuser before the eyepiece. So with that confusion of those, not sure what they are for or when to use them? I’m assuming it has something to do with the math formula of length. ( I do collimate too) I believe I do that right and have a nice collimating laser.
Very good video! Thanks!
Very good discussion on eyepieces. I learned a lot. Thanks for making the video. I am going to subscribe to your channel. Best to you.
A better and easier rule of thumb is 2x the aperture in millimeters will give you the maximum magnification, but of course that depends on seeing conditions.
Good stuff.
Benjamin if you have a Barlow that the opposite end of the eyepiece screws off you have a 3rd option if you screw that end onto eyepiece it breaks the mm down 1 more time.
really great explanation, thank you
Really excellent. If you did this unscripted you did a superb job
Great video - very helpful. Thanks!
Great video ☺
Thankyou ! As a novice , I needed this
Great 👍 job man very nice 👍 ⭐️⭐️⭐️⭐️⭐️
yes excellent video
Another great vid, keep it up :)
quite helpful, thanks.
nice video bro ,great looking telescope
Could a couple of possible advantages of using the Barlow that would duplicate magnification with other individual eyepieces be the use with a wider angle eyepiece, or one with longer eye relief? ....or even the larger orifice of a shorter eyepiece, like the difference between a 20mm Plossl and 10mm. I suppose stacking more glass might have some disadvantages, but ease of use and flexibility with FoV would seem to be worth it. Opinions?
HELLO,
IM A NOVICE AND CAME ACROSS YOUR VIDEO, IT HELPED ME ALOT.
QUESTION WHERE CAN I BUY THE " 20 MM XPLORER SCIENTIFIC EYEPIECE" THAT YOU MENTIONED IN THE VIDEO.
THANK YOU.
Thank you
i have an 8 inch dobsonian,its highest magnification is 480 ,what would be the best magnification range for this telescope to see planets
I have a Jason 408 mercury telescope which included the eyepieces(F-4mm and F22mm) that were included and I'm tired of them cause they lack eye relief. Which are the best eyepieces I need for that telescope?
Quick question 😆 moved onto a reflector 750pds now my eyepiece projection is too heavy so I got a badder click lock eyepiece holder now I have lost inwards focus by 20mm so I bought a Xcel 3 X Barlow use it on T2 adaptor question is its 2 powerful for moon I got 2 x crop on Panasonic Lumix g85 how do I decrease magnication of Barlow
Hey, I have bought 8 inch Orion Dobsonian telescope, in the package, I got one deep view eyepiece, 1.25 Barlow lens, and 25mm eyepiece.
Can you please suggest to me which other eyepieces I should buy to view crisp views of Jupiter, Mars, Saturn, and other planets.
Is it an astrograph or an ordinary dob ? I have an ordinarily 12 inch/1500mm dob which I am trying to use for short images and video.
The main question is how do you maneuver it ? cuz i have an 8 " dobs and bringing it outside every time is a pain in the back.I`m thinking about returning mine and getting something light like a refractor or Cassegrain any suggestion?
Good information for a beginner chosing simple eyepieces
I agree with all the comments here below... Very helpful for me as I am to get my first telescope this spring...
Da Lu what telescope did you get
Hi, i have Orion xt8 dobsonian and wanted to know, is Orion E-Series 7-21mm Zoom Eyepiece is better then individual plossl eyepieces. And please let me know eseries eyepiece are plossl, means crisp image as plossl eyepieces does.
Great video, Benjamin. Simple Suggestion: In the future you might want to add that great views come at a price, for such is the life of a star jock. The Explore Scientific 20 eyepiece you love is currently $450 at Amazon ($465 from the mfg).
well explained👍
Good video Benjamin!!! Forgot to mention that you really don't get the total of FOV that comes (AOFV) with your eyepiece because you still have to divide the AFOV in the magnification and then get the true field of view (TFOV)
Thanks so much!
Seem to have to add an extension tube to reach prime focus with a dslr.. my small canon s110 was able to focus on the moon attached to a 20mm plossi..
Your videos are really helpful for a beginner like me, make some more! Thanks
Great video ☺
Hi Benjamin, What magnifications do the Baader eyepieces give you ?
I've bought a GSO 10" dobsonian reflector a few days ago. I've only got a 10mm & a 15mm plossl eyepiece. There has been thick cloud since I got it. What lens would I need to find galaxies & nebula easily ? Would I need a 25mm or 32 mm while seeking the object then switch to a 20mm ? What eyepiece is best for the Andromeda galaxy ? If I wanted to reduce the cost would it be best to get a quality 20mm and cheap 25 / 32 mm ? Do people get more for their money using a 6" reflector with top quality eyepieces compared to a 10" reflector with cheap quality eyepieces ?
Hello zytigon. All good questions! The focal length of your scope is 1250mm, so the magnification of your eyepieces will be 125x for the 10mm (1250/10) and 83.3x for the 15mm (1250/15). It is important to remember that the Field of View plays a big role in the size of objects you can see with a certain magnification. For example I can see almost as much sky with my Explore Scientific 20mm with a 100° field of view as I could with the much lower magnification 30mm GSO SuperView (68° Field of View). They both have a TRUE field of view of 1.6°. Both the 25mm and 32mm GSO Plossl, provide significantly smaller True Fields of Blue (1° and 1.3°).
The Andromeda Galaxy is pretty big, so you would want the 32mm. I think that would be a pretty good eye-piece for other nebula and galaxies as well.
I think the 32mm would also be the right call for scanning through the sky. To be honest, I scan the sky with my binoculars to find object and then zero in on them with the telescope. With the Dob, the objects move through the viewfinder of the telescope very fast on high magnification (because of the rotation of the earth).
I like my expensive eye-pieces a lot more than the GSO. I think I would sacrifice the size of the scope a bit to own some higher quality eye-pieces.
I also think a good quality barlow makes all the difference ?
Cool video ☺👍:)
Thanks !!
I got a 5mm hyperion with the second hand 254 mm dobson I bought. I’m wondering with the other ones I should buy . Was planning to go for a 24mm and 13mm (both hyperion collection) before your video. But maybe I should reconsider to buy first this large field 100mm which looks amazing !
What do you think I should start with ?
I finally bought the 21mm, 13 and 5mm all hyperion, as I’m able to combine a several different focale length with them. It was more in my budget when I saw the price of this 100º field. Thanks for the answer
Hi! Thank you for such a comprehensive video! How does one know if the eye piece they're looking at is compatible with the telescope they have? Are there standard sizes or do you need to have a huge selection of lens adaptors? Just for reference - I am looking at getting the Sky-Watcher Flextube 300 SynScan Dobsonian 12-inch.
Many thanks!
Just saw your comment... better late than never! Stardards are 1.25 inch and 2 inch (0.96" is an old standard that you probably don't need to worry about with any new equipment). There are adapters you can get to go from both 1.25 to 2 and 2 to 1.25.
@@benjaminpoole9383 thanks very much!
I just want a good eyepiece for my xt6 enough to have a very good view of the outer and inner planets can any one of you help me out
Question....
Doesn't aperture create field of view?
If you have an eye piece with 100o field, it won't matter if your aperture only opens to 60o field.....
I love that 17mm you got. Great for my Mead ETX-125 and Zhumell 12"
78 Tranz Am Man how you like the ex125, i want to buy that one
Hello, regards, I would like you to record how each of your eyepieces looks on your telescope
Do you have a link for those eyepieces?
can you actually see up to magnitude 14 with a 12 inch dob?
Hi Benjamin! Thank you for your video! I have myself also Hyperions, 13mm and 36mm (great definition eyepiece!). I got some time ago a TV Delos 6mm, but I don't think its performance is a huge better than 13mm Hyperion with expander rings. Indeed great quality-price eyepieces!
I must say I find your telescope beautiful, are your views aswell as gorgeous? I have myself a Orion Mak 150mm, and even it I have very nice views, I was not yet abble to see difficult objects like Orion Horsehead, Rosetta Nebula, Triangulum Galaxy... Sombrero Galaxy is the very bright and nice exception. Were you already able to see these objects in such an 10' telescope? Best regards from Portugal!
Hi Ricardo! That is very interesting to hear about the difference between the TV and the hyperion. I've always wondered how much added quality you get. I haven't seen a lot of difficult objects. I know the horsehead nebula is almost impossible to see without perfect seeing conditions. My nephew managed to capture it in some long exposure pictures.
I've moved to Sydney so seeing conditions aren't nearly what they were in New Zealand when I made the videos! I really did enjoy that telescope especially with the hyperion and explorer scientific eyepeices!
Why couldn’t you see the Rosetta nebula? To dim I would guess? You got plenty of focal length.
Hello, please tell me what is the best eyepiece focal length to view the deep sky objects with?
Thank you
It really depends a lot on which object you are viewing and the apparent field of view of your eyepiece. Many deep sky objects are quite large, so a 30mm will probably be a good start. I have a 20mm with a 100 degree field of view and it works well.
Did it just go over my head? I wanted to know the difference between a Short telescope and one that is longer and what does fast vrs slow mean in relation to the length of the tube?
Otherwise, good job. Thanks
The length of the tube approximates the focal length, , so a shorter tube = shorter focal length. You ca now use that information about a long\short tubes focal length to work with his explanation, though its best to get the focal length from the manf. specification sheet. This video does not cover fast vs slow so you'll have to look else ware for that discussion.
Great vídeo Benjamin . Please do you believe It would be a good Idea to buy a 10 inch telescope instead of a 8 inch one? I am nota sure If the improvement justifies the extra money we would expend on a 10 inch. Thanks for any help
I think the 10" is worthwhile over the 8", but transporting it is quite a bit more difficult. If you're not going to be moving it around much, I would go with the 10.
Thanks for replying back. ALL the best.
Awesome video. I need that eyepiece...but 350.00 damn
I suspect my barlow is not of good quality. And the telescope is unbalanced and top heavy with a camera and a barlow and a heavy eyepiece..will try to put some weights on the bottom.
I have a question please help. When I look throw the eye piece I see blurry but once I remove the eye piece and I look inside the focuser I can see the moon pretty clear. I have a celestron astronaster 114
Hi Pedro, getting the telescope into focus can be an art, but also there are some things I can think of that would make it go wrong. First make sure that the eye piece is properly seated in the focuser. If so, you should try turning the focusing knobs on the focuser all the way in one direction and all the way in the other again to see if the moon starts to get in focus somewhere along the way. If it does get close into focus, most focusers have a fine adjustment knob that you can turn to really zero in the focus. Sometimes you may be turning the knob, but the focuser isn't moving in and out. In this case, for some reason the focuser isn't engaging with the knob. Another thing, eye pieces have different length of eye relief. Sometimes you need to be up to 20mm away from the eyepiece to get a good view.
Did you say that was 12 or 14" telescope???
Which leads me to ask? Which is better a 14 or 12" telescope for video and photography of Jupiter, Saturn, and Mars to start with???
How much did each bellow cost???
His telescope is 10/1250.
I was hoping you could explain why I saw an unobstructed view of the sky and then, the next time I brought it out, I could see the secondary mirror and its supports. Light source would be behind it but it illuminated the secondary mirror. I'm new to this and think I am doing something wrong.
I'm not 100% sure Michael. Possibly because of the way environmental light was shining into the scope. I'm not sure if you're collimation could be off and this is presenting the problem. I hope you find a solution.
I've had the same experience on a camping trip with my 8" Dob to look at the Persiad shower, Jupiter, Saturn, & Mars at it's largest this summer - no less. I hope to hear if you found the solution to this problem.
Does anyone know what type of telescope he is using. Also model #? I have seen it in a lot of videos. Thank you for the help!
www.gs-telescope.com/content.asp?id=115 The one I used was an older version of the one in this link.
Nice effort ..keep it up...Why do not you deal with real sky as well in your future videos..!
I just want to correct you on tge part where you said that the eyepiece changes focal length when barlow lens is added. Eyepieces does not change focal length but, instead barlow lenses makes your telescope focal length longer by 2 times
Great video! Have you ever looked at building a telescope?
I'm currently trying to.
What's a mear? Do you mean mirror?
My eyepiece is hanging out of my telescope.. help anyone?
Do you know where rule of thumb came from....?
Not sure who came up with it, but I think it mostly came from observations that around that magnification (60 X Mirror Diameter) and greater, a clear image could not be viewed.
how is it possible that it's focal length is 1250 mm? That's only 4 feet, it looks like the scope is almost 4 feet long and then it doubles back. I would think the focal length would be almost double that. What am I missing?
The focal length is measured from the mirror in the bottom of the telescope up to where in converges in front of the eyepiece. The light does indeed travel the length of the scope almost twice, but the focal length is only measured from the point at which it hits the mirror in the base of the scope and travels back up.
@@benjaminpoole9383 ohhhh ok I understand now thank you that makes complete sense!
Realy? If you are looking at a binary star system through your telescope you can see both stars indevidually? I didn't even think they could do that with the hubble
3:47
Hi Chris, yeah it is amazing how things we never thought possible of seeing can be visible with a telescope, or even a pair of binoculars! According to space.com (www.space.com/22509-binary-stars.html) 5-10% of binary stars are visual binaries. Here is another article that vividly describes different types of binary stars: www.atnf.csiro.au/outreach/education/senior/astrophysics/binary_types.html.
so looking online i can get an explore scientific 82 degree eyepiece for $160 and it costs the same for a 68 degree baader Hyperion eyepiece, is there any reason?
I'm not sure what the difference would be other than the expander rings on the Hyperion. Those eyepieces are versatile and give you a range of focal lengths. You're probably going to be happy with either piece, but the wider angled eyepiece can make for a nicer viewing experience.
the person who got me the telescope recommended televue panoptic lenses, they are significantly more expensive around $300, do you know anything about them, are they worth the extra money
btw i really appreciate the fast response time
I looked into the televue eyepieces when I was buying mine and they seem like the best quality you can get, but for me the increase in quality didn't justify the cost. I was able to more eyepieces that were still good quality. $300 seems inexpensive for a televue eyepiece however.
thanks so much for the help i might be back with more questions
No problem!
Is that telescope 10 inch or 12 inch?
10 inch
That is GSO 10" ?
RELI GI Yep, that's right.
looks like my astro tech , looking for a 2" zoom threaded eyepiece. Know of any?
Michael Del Rossa from what I can tell this baader zoom eyepiece is threaded. I've never used it, but I'm certainly happy with my baader products! www.baader-planetarium.com/en/baader-hyperion-universal-zoom-mark-iv-8-24mm-eyepiece-(1¼"--2").html
I was looking at that , might try the cheaper version mead first, thanks tho. Oh, can I ask you another question? I see your telescope is supported by the same frame I have, once the weight of the camera is on the end do you find it doesn't stay still? or how do you keep your telescope still?
Thank you.
Hi Michael, I have had problems with that. They make an adjustment on the telescope to rebalance it, but sometime it isn't enough. On my telescope I just took some paperback books and a big rubber-band and attached them to the back end of the telescope as a counterweight. On the telescopes I bought for my nieces and nephews, they were always unbalanced. I bought some large magnets to use as semi-permanent counterweights.
I suspect the Explore Scientific will cost about the same as my first telescope :)
I have eyepieces that are worth significantly more than my telescope.
Well how much is that eyepiece collection worth?
I think around a grand.
If baader hyperion 13mm is good in 10" GSO?
RELI GI I'm sure it would be just fine.
Benjamin Poole Ok, thanks i dont know what should i buy in 10" Baader hyperion 13mm or ES 14mm? I dont have too many money :(
RELI GI Well, the nice thing about the basket eye pieces is that you can use the expander rings to increase the magnification. I can just see the whole moon in the 17mm badder Hyperion, but I like to use the 8mm to look at planets. With the thirteen you'll have trouble seeing entire large objects, but you can use the expander rings or a barlow to see Saturn and Jupiter pretty well.
Benjamin Poole thanks, but on deep sky Baader hyperion is good? because i dont know what should i change.
RELI GI yeah, it should be just fine