turboscrew

I got my scope (300 mm / 1200 mm F/4) last June, and everything looked good, but a couple of days ago I noticed that the mirror had started "pinching". I took the mirror off from the cell. I thought there might have been too much silicon between the support pads and the mirror. I carefully took off all silicon from the supports and the mirror, but I'm still not convinced that it wouldn't pinch if I put it back. Does anyone have advice or pointers about how to mount a mirror into the mirror cell and how to do the adjustments? Originally the floating supports (the two outer pads in each triangle) were glued (or siliconed) to the back of the mirror and even the holders were glued to the side of the mirror, My mirror cell looks like this (IMG_0637.JPG). The holder bolts are slightly conical and so is the hole in the holder (doesn't show that well in the picture IMG_0642.JPG). The hights of the holders are not adjustable, so the the mirror height needs to be adjusted instead (IMG_0640.JPG). The middle bolt under the support triangles adjust the height of the triangles, and the white plastic pads can be adjusted as well. The other two bolts under the triangles just limit the triangles' lateral movement.

That's a great chart!

I found this: https://www.saao.ac.za/~wpk/exposure.html but I think the 'K' here is actually L/C, where L is target luminance and C is equipment specific(?) "calibration constant". I wonder if I'm getting closer? I also wonder if I can find (average) luminances of planets somewhere?

I wonder if I could find some beginner's tips about digiscoping somewhere? I was planning of trying Mars through my 12" F/4 tube. How do I find some good starting values for the camera settings? I have Canon A590, and it has manual mode. I also have CHDK for it. I could try with partly automatic, but because the camera won't show what values it has chosen, I wouldn't learn a thing that way.

Ordered the mount and tri-pier. Now nervous waiting begins...

Thanks. I'm after an encoderless version.

Do you think CEM120 is OK for Orion Optics VX12 for some firt steps in AP later? Is there something I should be aware of, that might make the mount unsuitable for me? I'm planning of getting a Tri-pier under it.

Thanks! I think that should do it.

I've been trying to find M51, M101, M81 and M82 without luck. I have 300 mm F/4 tube, so I think I should be able to tell if I see them. I've tried with 25 mm eyepiece (48x), but either not found them or not recognized them. Any advice? I could find M57 quite easily. Also, do you think that replacing my current 6x30 finder with, say, 8x50, would help? I'm going to replace it anyway because I'm not a yogi that can bend enough to look into straight finder scope end that's 4 inches above my navel. (Hmm, maybe I should add my gear in the signature...)

No, not all. I'm just heading there...

Just for info, I tried out both Astronomy Linnux 18.04 and Debian Linux 10 with Astro pure blend. I'd recommend Astronomy Linux, because it has more, and more modern tools, and Debian has suddenly become quite heavy. And Distro Astro has been dead for a while.

Well, about 100 km from where I live.

I think for the OP's tube that probably works well. Congrats for a nice scope. F/5.9 nice for both planets and DSOs, and it's not that picky about eyepieces. I wouldn't recommend Baader Hyperions for F/4 tubes, but for about F/6 tubes, I think they work fine. I don't have that zoom (nor other Hyperions), but I've heard that it gets very stiff when it's cold - less than -10°C. Keeping it in your pocket for a while is said to help. I have heard a lot of good words about the zoom.

Some people refuse to look at anything below 30°. Low at the horizon you can really see good images - in fact many of them, of different colours and on top of each other. The atmospheric dispersion... 😉

Also, I'm not that convinced that alt-az is so much easier. You don't really have to polar align it that well, if you are only doing visual. With rough alignment eq mount probably works a bit netter than alt-az. Both have singularity, but in different point. Basically alt-az is eq with latitude set permanently to 90°. Note that very few eq mounts allow 90° as latitude. Typically the adjustment range ends at 65°. Then again, OP may have different opinion about eq v.s. alt-az.