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.

You might want something with a bit longer focal length, if you are after a telescope for both seep sky and planets. F/6 .. F/8 would be better. Slower scopes also are usually more forgiving. Scopes with F/9 and greater are usually used mostly for planets. On the other hand, I'm painfully aware what Corona has done to the selection. These days you can't always get what you want, but have to settle with the options still available.

The BST Starguiders are meant for F/5 and slower.

About the eyepieces: watch out for F-ratios the eyepieces are meant for. On the FLO pages it says about BST StarGuide eyepieces: "Suitable for use with telescope focal-ratios f/5 and above". That is, not for OP nor me. Plössls work fine with even fast scopes, but there is a dependency between eye relief and focal length. That's why <5 mm focal length Plössls are not abundant. Their eye relief begins to be painfully small. Also orthoscopic are good. Plössls and orthoscopics are not very expensive either. Usually wide angle eyepieces have so many lenses that they tend to be suboptimal for fast telescopes. My tube is 300 mm / 1200 mm, F/4. I can relate to the OP's pain. My latest purhases are TeleVue Plössl 15 mm and Baader classic ortho 6 mm, but I'm still under new equipment curse.

Well, my yard is somewhat well "hidden" from the winds, but I don't have dome, or any kinds of walls, so I think I should go with CEM120. It would be quite a hit to realize, that I had spent almost as much money to something else that is not quite adequate. (Searching for tissues...)

I think you have at least some experience with VX12 on NEQ6. What did you discover? I think I'll follow your lead...

Hmm, how does that work? Is it still 18 kg for imaging in EQ mode? I've seen that I really want a tracking mount and stop loosing the objects while changing eyepieces. My dobson is not that smooth in any case, so I think EQ would be good even if quite expensive. Hmm, in the instruction manual linked in the page, it says that the payload is 20 kg??? And it says the same on Sky-Watcher's page. I was originally thinking about EQ6-R, but it, too, has too low load capacity.

It's just that the mounts are quite expensive. So I can't afford to put 1000€ more for "just in case", but even less I can afford almost as expensive mount that's almost usable. I guess CEM70 is so new that there is not much experience of it's limits in real use yet. Even the reviews mostly seem to echo the marketing material.

BTW, since CEM120 has Losmandy style attachment, do you know which dovetail is needed? I'm thinking about the length. https://www.orionoptics.co.uk/ACCESSORIES/attachmentplates.html

OK. Basically CEM120 is the minimum, really - in open, but less windy field? And CEM70 would be enough, roughly, only if there are walls around to protect the whole from winds? Actually my yard is quite protected from winds by trees on my neighbours properties. The trees also act as a safe guard keeping me from trying to see objects below 30°. (Well, there are some "holes in the barrier" allowing me to see even downto about 20°)

I've been planning of getting an EQ mount for my OrionOpticcs VX12. I wonder if CEM70 would be enough for occasional photography, or should I weep and go for the (much more expensive) CEM120? The VX12 is this (not the 'L'-version): https://www.orionoptics.co.uk/VX/vx12-12l.html