barbulo

Backlash is the mechanical lag between when the gears start to move and when the scope effectively starts to slew. I am not familiar with your mount, but the movement you mention could be caused by some sort of protection or limitation that prevents the scope from aiming below the horizon. Let's leave it to the experts to assess.

Concur with @powerlord: good piece of gear. I use an A4 one for my 6" Newt and works pretty well with a white t-shirt. Has 3 levels of brightness and is powered via USB.

Thank you @wimvb , tilt makes much sense. I've noticed the same pattern with different targets. And the optical train seems to be firmly hold. My suspicion is that the tilt is caused by the 2 thumbscrews when tightened. I could try inserting the MPCC in the barrel using Teflon tape instead of the thumbscrews. Then I would choose a target that allows the camera to be in a safe position and where gravity has less influence. Makes sense? EDIT: I've just came across these threads where the problem is tackled using a third thumbscrew:

Hi and welcome to SGL

Hi all, With my current setup, CANON 600D + MPCC MKIII in a SW 200PDS with its stock 2" barrel (2 thumbscrews), I'm experiencing some residual coma (the image depicts the 4 corners and the center of a picture taken recently). As you can see, the coma is more evident in the upper corners. I've tried a meticulous collimation (visual + laser) and measured the optical train backfocus (55mm according to Baader specs). Yesterday I tried turning the camera 180°, and it happened that the coma appeared at the bottom of the image. With this test, I think I can exonerate the MPCC. Moreover, I realized that the MPCC doesn't fit exactly squared in the 2" barrel when tightening the 2 thumbscrews. Now the questions: Could a small misalignment of the optical train cause this coma? Would a compression ring like this one, be helpful? Searching for the benefits of compression rings, some people in SGL and CN say that the compression ring do not center the optical train. However, I think that it is no a matter of centering but squaring. Any thoughts on this? Anyone with a comparable setup has experienced something similar? Thank you very much in advance.

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Hi and welcome to SGL

Welcome to the Lounge!

Hi and welcome to SGL.

Welcome to the Lounge!

Hi and welcome to SGL

You can try PHD2‘s different alignment methods.

Welcome to SGL

Nice thread! Good to have it re-floated. I've always liked to gaze up, at the dark night sky, the moon or even at clouds or airplanes. My kids received a telescope last Christmas, and was then when the bug bit me deep. We soon upgraded the gear, and now I spend the scarce clear nights trying to pick "digital glimpses" of our universe and absorbing bits of knowledge from this forum the cloudy ones. BTW, thanks to all the helpful people of this forum. Keep goin'!

Just try to skip this step.

Thank you very much @discardedastro I’ll get a Cheshire and do some corrections in the MPCC backfocus distance before giving up.

No, I don’t. I’ll have to get one.

Thank you all. I forgot to mention that I used a laser collimator and that my purpose is AP. I’m also dealing with traces of coma in my pictures (backfocus?) so I need clear skies to check.

How do your experienced eyes see this collimation?

I had the same problem you have but with a EQ-3. I only managed it to work when removing the ST4 cable guider-to-mount. If you prefer to keep it, then you should NOT connect the Synscan to the PC, and do the star alignment and GOTOs from the hand controller. If you connect the cam both to the mount and the PC (being this connected to the Synscan), it will duplicate the orders given to the mount. Hope this helps.

Yes @Iem1, I would like to mod it some day. It will surely make a difference with nebulas. Regarding the ISO, I also read about 800 as the sweet spot for the 600D, but I decided to use 1600 for fainter objects. It will be a matter of trying and checking. However, I'm greatly concerned about the remaining coma. It annoys me a lot. Yesterday I tried to re-collimate the telescope but it seems I cannot get rid of the artifact. I'm starting thinking that the MPCC has something to do with it.

Then try connecting the guide cam only to the PC, and let PHD2 drive the guiding from the PC to the mount.

If you disconnect the mount (Synscan HC) from the PC, where do you connect the guiding cam? To the mount or to the PC?

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Just match the position of Polaris in the polar scope as shown in the APP.