Trying a new imaging train setup that will avoid collisions with the equatorial wedge and telescope base. Also, video shows what I have on the telescope.
To solve the balance issue near the zenith you need to change out a barrel weight to a pancake style weight that can hang down away from the OTA counterweight rail. Your diagonal needs to be aligned so that it is 180° to the counterweight track. Adjust the pancake weight distance from the center axis to counteract the optical centerline offset of your imaging gear caused by using the diagonal. The distance from the fork OTA axis and the offset from optical center is very sensitive to position because the torque varies with the square of the distance! To maintain balance from 0 -> 90° Dec the mass of the counterweight and offsets of the center of mass from both the Dec axis and optical centerline should match as closely as possible the center of mass and offset of the imaging gear. Obviously it won't be exact.. in fact, you'll want to have some bias either nose heavy or tail heavy to ensure the drive train is under oad at all times to avoid backlash float. The same is true for the RA drive train. Add a small weight to one fork arm a needed to keep the RA axis under load and avoid going through a balance point where the backlash causes float or shifts bias as you track your target. The barrel weights are mostly useful for offsetting finder scopes. Any gear mounted further away from optical center needs the 2 axis offset of the pancake system. I see you have some gear attached to one fork. Be mindful of the effect of this weight as for a 10" OTA it's riding about 7" offset from the RA center of rotation. The forks start out unbalanced with the DEC drivetrain and clutch plates being in one side, and that is intentional as it keeps the RA drive loaded. Your add on may cause a zero balance point in RA motion unloading the drivetrain or overload it. Neither is good for guiding. If you're getting times or parts of the sky when your images look bad or guiding freaks out, this is probably why. The other problem you are sure to encounter is flexure in your imaging path due to the use of slip fit attachmenta that are only designed for visual use. They will slip and they will sag when you attach heavy cooled cameras with spacers. The Meade microfocuser can be configured with threaded attachment on both sides. But watch out for adapters with restricted internal optical path. Find a diagonal with removable barrels that you can replace with threaded adapters/spacers. The Meade SCT was designed around a 105mm backfocus. As you discovered, the effective focal length decreased as you increased the amount of backfocus distance. It also reduces the image circle size and brightness. Hopefully you've already changed the backplate to rid yourself of the SCT 2" threaded interface with its small 37mm clear optical diameter. You should be able to get APS-C sensor coverage with minimal light drop off if you maintain 48mm interfaces throughout and are careful to find a diagonal with a large clear optical path and standard thread sizes. Although once your added the diagonal is tempting to relax about spacing within the limits of the OTA focuser, it's best to keep things as short and tight as possible. Long focal length helps a bit with tilt and sag, but vibration and light drop off with long backfocus more than offsets it. Great creative idea to image near the zenith especially for those with bad seeing and light pollution! Thanks for posting. I like your rig. I'm partial to Mead optics 😁😁😁 2:54
Thank you for the info and reply. I will look into that weight system. Lots of info to take in for sure. I have been trying to get better tracking for many years now. The LX was my first big purchase back in early years of 2000. There are times I got really nice pictures with the telescope but that mostly occurred at the club's dark site.
I welcome recommendations about getting my rig to track better. I re-read your suggestions and did some searching on the pancake weight system you mentioned. I assume the weight system you are suggesting is the one where the pancake weight can be screwed in and out on the treaded bar that is connected to a dove tail plate that is connected to the bottom of the telescope. Is that correct? Is there a potential problem with the projected pancake weight and its threaded bar colliding with the wedge’s sides? I saw a system that listed for a Meade 10” LX and got a sticker shock. I moved my Dew Buster controller to the East arm to add weight to that side. I read that the east side should be a little heavy when balancing the setup, so the gears are engaged. I realize that when that side slews to the other side that feature is probably not working. As for the rear cell items, I have not changed anything out from what the telescope came with when I purchased it new twenty years ago, other than Bobs nobs for collimation and Peterson Precision kits for the gears from Nylon to metal and a focus knob upgrade. The opening of the rear cell attachment piece is original and does have a 37mm opening but I need that piece to attach the Microfocuser’s adapter ring for the Microfocuser’s connection. It did not occur to me that beyond the 37mm opening I had 48mm openings to the camera’s sensor. However, the camera’s sensor is nowhere near 48mm wide. As for the back focus of 105mm, Meade tech people told me not to worry about back focus unless I use the 6.3 reducer, then the 105mm would apply from the glass of the reducer. I had asked them about both the 55mm and the 105mm back focus last year. I did put a small amount of tension on the Microfocuser’s ball bearing set screws. I also tightened down the nose pieces on the 2” diagonal. The last few nights that I was using the vertical setup, I did not experience any slippage or rotation as I did a few months ago when I first tried the vertical setup.
Seeing conditions in my backyard are Bortle 7 and at the club field it is Bortle 4.5. But my backyard is getting worse I think on light pollution. I have noticed in my backyard that EAF and plate solving has more failures than at the club’s field and the light pollution filter does not help in the backyard either. The light pollution filter may help on taking pictures but the EAF and plate solving it does not.
To solve the balance issue near the zenith you need to change out a barrel weight to a pancake style weight that can hang down away from the OTA counterweight rail. Your diagonal needs to be aligned so that it is 180° to the counterweight track. Adjust the pancake weight distance from the center axis to counteract the optical centerline offset of your imaging gear caused by using the diagonal.
The distance from the fork OTA axis and the offset from optical center is very sensitive to position because the torque varies with the square of the distance! To maintain balance from 0 -> 90° Dec the mass of the counterweight and offsets of the center of mass from both the Dec axis and optical centerline should match as closely as possible the center of mass and offset of the imaging gear. Obviously it won't be exact.. in fact, you'll want to have some bias either nose heavy or tail heavy to ensure the drive train is under oad at all times to avoid backlash float. The same is true for the RA drive train. Add a small weight to one fork arm a needed to keep the RA axis under load and avoid going through a balance point where the backlash causes float or shifts bias as you track your target. The barrel weights are mostly useful for offsetting finder scopes. Any gear mounted further away from optical center needs the 2 axis offset of the pancake system.
I see you have some gear attached to one fork. Be mindful of the effect of this weight as for a 10" OTA it's riding about 7" offset from the RA center of rotation. The forks start out unbalanced with the DEC drivetrain and clutch plates being in one side, and that is intentional as it keeps the RA drive loaded. Your add on may cause a zero balance point in RA motion unloading the drivetrain or overload it. Neither is good for guiding.
If you're getting times or parts of the sky when your images look bad or guiding freaks out, this is probably why.
The other problem you are sure to encounter is flexure in your imaging path due to the use of slip fit attachmenta that are only designed for visual use. They will slip and they will sag when you attach heavy cooled cameras with spacers. The Meade microfocuser can be configured with threaded attachment on both sides. But watch out for adapters with restricted internal optical path.
Find a diagonal with removable barrels that you can replace with threaded adapters/spacers.
The Meade SCT was designed around a 105mm backfocus. As you discovered, the effective focal length decreased as you increased the amount of backfocus distance. It also reduces the image circle size and brightness. Hopefully you've already changed the backplate to rid yourself of the SCT 2" threaded interface with its small 37mm clear optical diameter. You should be able to get APS-C sensor coverage with minimal light drop off if you maintain 48mm interfaces throughout and are careful to find a diagonal with a large clear optical path and standard thread sizes. Although once your added the diagonal is tempting to relax about spacing within the limits of the OTA focuser, it's best to keep things as short and tight as possible. Long focal length helps a bit with tilt and sag, but vibration and light drop off with long backfocus more than offsets it.
Great creative idea to image near the zenith especially for those with bad seeing and light pollution!
Thanks for posting.
I like your rig. I'm partial to Mead optics 😁😁😁 2:54
Thank you for the info and reply. I will look into that weight system. Lots of info to take in for sure. I have been trying to get better tracking for many years now. The LX was my first big purchase back in early years of 2000. There are times I got really nice pictures with the telescope but that mostly occurred at the club's dark site.
I welcome recommendations about getting my rig to track better. I re-read your suggestions and did some searching on the pancake weight system you mentioned. I assume the weight system you are suggesting is the one where the pancake weight can be screwed in and out on the treaded bar that is connected to a dove tail plate that is connected to the bottom of the telescope. Is that correct? Is there a potential problem with the projected pancake weight and its threaded bar colliding with the wedge’s sides? I saw a system that listed for a Meade 10” LX and got a sticker shock.
I moved my Dew Buster controller to the East arm to add weight to that side. I read that the east side should be a little heavy when balancing the setup, so the gears are engaged. I realize that when that side slews to the other side that feature is probably not working.
As for the rear cell items, I have not changed anything out from what the telescope came with when I purchased it new twenty years ago, other than Bobs nobs for collimation and Peterson Precision kits for the gears from Nylon to metal and a focus knob upgrade.
The opening of the rear cell attachment piece is original and does have a 37mm opening but I need that piece to attach the Microfocuser’s adapter ring for the Microfocuser’s connection. It did not occur to me that beyond the 37mm opening I had 48mm openings to the camera’s sensor. However, the camera’s sensor is nowhere near 48mm wide. As for the back focus of 105mm, Meade tech people told me not to worry about back focus unless I use the 6.3 reducer, then the 105mm would apply from the glass of the reducer. I had asked them about both the 55mm and the 105mm back focus last year.
I did put a small amount of tension on the Microfocuser’s ball bearing set screws. I also tightened down the nose pieces on the 2” diagonal. The last few nights that I was using the vertical setup, I did not experience any slippage or rotation as I did a few months ago when I first tried the vertical setup.
Seeing conditions in my backyard are Bortle 7 and at the club field it is Bortle 4.5. But my backyard is getting worse I think on light pollution. I have noticed in my backyard that EAF and plate solving has more failures than at the club’s field and the light pollution filter does not help in the backyard either. The light pollution filter may help on taking pictures but the EAF and plate solving it does not.