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He caught covid - it’s badly affected his logic, memory and love of lens licking 🙂 Get well soon Mike 👍

Looking forward to the responses as I have one that needs sprucing up …

1. I opened up the azimuth motor compartment and check everything for slipping. I could see wormwheel running fine It didn't solve the problems. 2. I opened the gear box, all ok. It didn't solve the problem. 3. The motor itself seems to function ok but could it be something to do with the encoder? I can see the wormwheel running but the large disc or platform is not turning. It can turn with the hand controller. So if it is not slipping is it likely the stepper does not provide enough torque? Ie is it gone? Thoughts on a replacement for it, assuming it's the culprit?

In truth stars will have an acceleration component to their motion for a number of reasons; for example the rotational motion around their galaxy's centre of mass. That change in direction by definition means the velocity is changing (even if there was a constant speed), in turn by definition acceleration. This is what we measure when we detect a star's radial doppler shift as it rotates in its orbit around the centre of mass. So at some point we will detect a red shift and at others a blue shift, and inbetween a changing red and blue shift. A star that is not gravitationally bound to its galaxy, so called rouge or intergalactic stars, will travel through space at a constant speed unless they come into the influence of say a black hole or other concentration of mass. Here the star will similarly accelerate until it either collides or is caught in orbit. But a star that is accelerating like that, say along our axial line of sight, would present with an ever changing red shift/blue shift. Just as you said red shift can also be caused by the cosmological expansion of space (recessional velocity) independent of the star's relative motion to us due to its motion through space. I'm not sure how they differentiate between the two, most likely the red shift due to expansion is a known component and rather like a background count rate of radiation it can be separated from the "motion" red shift - I guessing here. We need an input from Andrew S here. Jim

I’ve got an old Vixen cwt that I want to spruce up as it’s seen better days. I don’t want the original Vixen green. I’m thinking black or silver. Perhaps white. Which type of paint should I use? I want something that won’t rub or flake off. I seek a nice finish.

The SM125 is becoming more appealing to me each passing day.

With the 150 Maksutov you shouldn't need any extension pieces to achieve focus due to the large focus travel of the telescope. When setting up for the moon I set the exposure to 15-20ms which is still too much for the capture process itself but is fine for locating and centering the moon on the laptop screen. Once centered I reduce the exposure to 4-8ms depending on how bright and large the moon is. You can also change the gain setting along with the exposure so that you get a good histogram reading and a clear image on screen. This is a good time to focus on the surface details of the moon as good focus is crucial for a sharp image.Once this is achieved you can then start the capture process.

Actually, this is very interesting, as I've wondered why manufacturers don't do the same to avoid spiders in commercial scopes.

My 152 Achro is fine for sweeping star fields, but so is a 6" f/5 Newtonian which is much lighter, cheaper, and color free. The 152 does very poorly on planets and double stars at moderate to high power thanks to excessive CA. DSOs appear about the same as in the Newt. @Stu1smartcookie What exactly do you find the 152 Achro to do particularly well or better than other comparable scopes? The only thing I've found it good for is extreme testing of violet-cut and red-cut filters to find out which (combination) yields the best image of various objects. Because I love tinkering with optical combinations, I find it fun. I'm trying to justify why I'm holding onto it.

Warning! I think someone might have hacked Mike’s account 🫣

I'm not sure that OP is concerned about origin of motion, but rather the fact that there is no preferred direction. If you look at this post: I believe it shows what is the heart of the question. We tend to study stars from earth and study their motion relative to us. Someone else might see different motion - after all motion is relative, and their Doppler shift would be in agreement with what they observe - as movement is relative.

And a first RGB-HOO processing attempt

I tried them both in the 72ED, 90 APO (both with TSFLAT2 field flatteners), 8" Dob with GSO CC, and 127 Mak. I don't think I had the 6" f/5 Newt or 152 Achro at the time. Both performed pretty consistently across all of them except for the slow Mak which closed the gap between them. I will say the background seems darker in the NT4 than the Redline. It might be for the same reason as with the Vixen LV line appearing darker: the use of rare earth glass types that contributes to their higher prices relative to their competitors.

Sorry Dizzy, it’s been a while but the night is yet young. FC 100DZ

They are all accesible in the Indi Control Panel, but I guess you are familiar with that if you have used this software before. When it comes to odd equipment, I sometimes spend a little time searching for clues regarding chipsets and such. (sudo) lsusb and dmesg are two terminal commands that can help. Then it's google. PS: It don't hurt to present the camera with another driver. These things are not written in stone. One thing is the outside, the inside can hide parts and electronics used by other manufacturers. If it works at all with another driver, try to tweak it. Things to do on a cloudy night.

John. Many years ago my first SW120ED was the gold version, an ex-demo one from Widescreen. In fact I was comparing it with Mike's TV101 at my home with Mike shortly after I bought it. The next day he advertised his TV and bought a new 120ED! In my memory it was excellent, as good as all the later editions including the Equinox which I've had at some time.

I think the ED80, 100 and 120 will still use FPL-53 plus a schott element, despite the above 🙂

I agree that redshift/blueshift don't need acceleration (as Jim also points out) but a body's proper motion does, surely, need to originate with an acceleration? What I'm getting at is that the OP's question is about movement since he asks in which direction the stars are moving. Is there not a fundamental difference between a body 'moving' because of the expansion of space and 'moving' because it has, at some point, been accelerated? If not, why do cosmologists distinguish between Doppler and Cosmological redshift? Olly

I totally agree with you regarding this. More often it's matching the element types together that proves to be more crucial. There's apparently little difference between the refractive index of FPL53 and FCD100 anyway.

The area looks about like this: There seems to be some uncharted nebula also in Ha at ~07h, 18deg DEC This time I didn't restrict too much my search on https://planetarynebulae.net/EN/page_recherche.php, but I still could not find anything.

Having used a number of old ED's, even from long established top end manufacturers, knowing the glass type isn't a big thing to be honest. The old Vixen 102ED didn't disclose the glass type as far as I'm aware, yet when my friend Derek bought a 102ED F9 we were both blown away by its stunning definition on Saturn (c2004). The colour correction on that scope was equally impressive and almost indistinguishable from the legendary FL102. When Derek told me he was about to exchange his 102 ED F9 for a 102SS ED F6.5 I was convinced he was making the biggest mistake of his life. He made the change anyway and I was proved wrong yet again. The 102EDSS was stunning both as a rich field scope and for lunar and planetary. I'm not sure if the Vixen ED's used FPL51 or an equivalent but the point is it didn't make a jot of difference. The scope was a jewel. So I think we should trust the choices made by the optical designers and the skill of the optical engineers and just enjoy the great scopes they provide us with.

Are you saying we need more than one telescope John? 😊

Doppler redshift is a measure of the stars motion due to velocity not acceleration. and it is measured along the axial line of sight. However stars also have a tangential velocity from which it derives "proper motion" To determine the combined motion of the star one would need both properties. Typically a measure of the star's proper motion would be taken by position measurement taken a few years apart. So to answer the OPs question if both stars show red shift then all we can conclude is that their axial line of sight motion is away from us. To determine their true motion relative to Earth would also need information on their tangential velocity. Jim

Thats my experience with refractors as well. I don't have an F/5 newt to try it out in now.