ollypenrice

Not really my thing but my few forays into lunar mosaics were done by eyeballing (like my many deep sky mosaics) and combined simply in Microsoft ICE. I couldn't fault it on the moon, though I wouldn't use it for deep sky. Olly

Peltier cooled camera every time for me. CCD cameras on the used market are becoming bargains and they still take great photos. Olly

I should have thrown in another snippet of information which we've found out: the edge and corner stars need focus to be bang on. When it isn't, the first thing we notice is not a loss of sharpness in the stars but elongation along one edge and/or in the corners. The stars can look pretty sharp in the middle and bad at the edge but further refinement of focus can fix it. I've never seen this before. Olly

I used to use the shower to loosen particles and rinse our 20 inch mirror. I'd get the water to room temperature and then let the motion of the water do the work. I'd then use distilled water with the usual mix of isopropyl alcohol and detergent in it as final clean and then rinse thoroughly with de-mineralised water because there's a lot of calcium here. As others have said, if the dust is sandy it shouldn't be removed with a wiping action. Use dabs, changing the cotton wall after each one. Olly

That's a bit close. Don't you know anyone with a longer interior space? I used to have a friend with a... well... condom warehouse... who let me use it for star testing. I'm sure other warehouses would also do! I don't know how well an artificial star would work for collimating the RASA but it would be worth a try. Firstly, though, you really do need a jig such as the one in the thread earlier. Olly

It's a fickle beast in my view. I had camera from the one based here on the tilt jig again because our stars have gone off along one side. You really have to get everything right on the RASA, notably collimation and tilt. This is not a scope which is going to like lots of random spacers, etc... The Artsy adapter dispenses with the pads which troubled Tomato, above. Have you collimated it? The only sane way to do it is with a small cylindrical camera (we used our guide camera) which lets you get at the collimation screws while still in situ. When it's going well the RASA is formidable, though. Olly

I was running one happily in SGP until it went back to its owner very recently. Good camera. Olly

You can buy pet warming pads (no, seriously, you can! 😁) which consume minimal current but produce enough heat to raise a small volume's temperature above the dew point. I dare say a dewheater strip would do the same. Your cover is waterproof and insulated enough for this to be worth considering, I think. Olly

One of the all-time great songs. ironical, sincere, funny... it has a bit of everything. One of my former students, now in their fifites, reminded me that I used it as a launch pad for teen romance stories once. Some of the creative writing they produced was quite... educational. What, risks in education? Yes, we used to take them... Olly

But you did want to use it for imaging if I read your post correctly? Olly

The 'imaging and visual' scope is a snare and a delusion. It doesn't exist. Don't search for it! (For imaging, you don't need aperture. For visual you do. For imaging you do need a driven EQ mount. For visual you don't. Even if you did find this mythic beast, once you had persuaded it to work for imaging the last thing in the world you would want to do is disturb it by converting between imaging and visual. The golden rule of imaging is to get it to work and then leave it alone!!!! 🤣 ) What does exist is the large Dob for visual. It will remain as good as it always was whereas imaging gear comes and goes and you may want to vary it in order to have a change of target, etc. Olly

There's no reason whatever not to guide with a camera lens. Plenty of imagers do it. It's just less common now that cheap, small guidescopes have entered the market. Lenses will need stopping down but the use of a home made aperture mask avoids the multi-blade diffraction artifacts. You can also use stacked filter rings but cardboard is cheaper! I agree that the Samyang is a killer lens but it has a very different focal length, and is a very different price, from the OP's starting point. It would be my choice too, though, for a small mount. Olly

I'm in France and a quick look at the Pierro Astro website suggests about 350 euros for this scope and Starizona flattener. An ultra-quick search on the net found a used Canon 200mm L seires prime lens for a good bit less than that. I only guide with my Evoguide and have never considered imaging with it but I have to say that I'd think hard about a 200L series Canon or other good, older prime lens. I've done deep sky imaging with a 200L and it was pretty good... Olly

Super. It's great to get such a good view of irregularities in a galactic plane. How 'ethical' do you want your background sky to be? There are ways... lly

Hardly surprising since it's a trackless waste....* The notion of a past, a moving present and a future is known to philosophers and theoretical physicists as The Tensed Theory of Time. Your Douglas Adams quotation tells us why! (Trivia: one of my best friends was at school with Douglas Adams but, prodigious as this information is, it must take second place in my repertoire to the fact that my cousin is the bass player in Jethro Tull.) Olly * of time...

Tracey: This is Tracey of the wheel clamping agency. How may I help you? Dr Who: Ah, my vehicle has been clamped and I need to liberate it. Tracey: Where did you park the car? Dr Who: I prefer to call it a vehicle. It's in one of the outer arms of the galaxy Beta Centuron. Tracey: Do you have the postcode? Dr Who: No. Tracey: I see. So when did you park the vehicle? Dr Who: Tomorrow. (From a radio comedy series on the UK's Radio 4. Tracey was a real person at work and the guy doing Dr Who got the voice just right. At some point in every phone call the victim would ask the caller's name and be told, 'The Doctor,' at which point they would invariably ask, 'Doctor who?' 🤣lly

Careful: some lenses (notably oil-spaced ones) don't like to be put in the sunlight and I seem to think that the same is true of Petzvals, of which Rodd's Tak is an example. I can't remember where I came across this information but since I have an oil-spaced triplet and a Tak Petzval I made a mental note of it. Rodd, check before you try it! Olly

Regarding backfocus, SCTs are very tolerant of variation, unlike faster systems. The consequence of changing the backfocus is that it changes the degree of focal reduction. Many SCT imagers plate solve their images to find out the true focal length of the reduced system. Olly

Image circle issues come in two kinds, vignetting and stellar distortion. There's not much you can do about distortion but flats fix vignetting to an astonishing degree. You'd first need to know how much you're prepared to tolerate. On a full frame chip a certain Tak FSQ106N 😁 has about a 23% light fall off in the corners but flats completely correct that. I used it more for mosaics than anything else and putting them together was easy, showing that the illumination ended up even. The other way to confirm this is to stack a set of flats using flats to calibrate them. I do this when demonstrating to beginners the purpose of flats. The output image should be (and is) almost perfectly flat. Olly

I suspect the 11 inch HD might actually be easier to use than the C8 which needs a flattener... You have the OAG projecting into the middle of the long side of the chip, which is good. Did you also push it in as far as you could then back it out by the smallest possible amount? You can do this using a light source of the kind you'd use for flats. You just want to see the start of the OAG shadow then raise the prism very slightly so you don't. It's vital to get it as far in as you can. Binning the guide cam will reduce its resolution but increase its sensitivity to light. You have plenty of scope for reducing its resolution without its being inadequate for your guiding purposes. You can measure your vignetting simply by comparing the ADU of a flatfield sub in the corners and then in the centre. My Tak FSQ with full frame camera saw a 23% drop-off in light in the corners but flats eliminated it. It was absolutely not a problem. Olly

Good question! I shoot in RAW and, as a Canon user, open the results in Canon Digital Professional, choose the ones I like, save them as TIFFs and then take them into Photoshop and/or Lightroom where I'll work on them - but only to refine them. I convert them to ProphotoRGB colourspace and convert to sRGB for the net versions. Nothing like the level of input that goes into astrophotography. A typical Lightroom adjustment for me, with a single exposure 'regular' daytime shot, would involve small adjustments to colour temperature, vibrance, hue and saturation, 'texture' (I like that one in LR but don't know what it's really doing) and some selective sharpening. I think a lot of people looking at the 'before' and 'after' might ask, 'What's the difference?' (As a processing-intensive astrophotographer I'm a sucker for more complicated kinds of daytime photography, notably focus-bracketed macro and HDR composites for some targets.) I'm useless at the 'spot it and grab it' kind of thing that street photographers do. I have to think about a picture for half an hour before I can take it! Olly

It seems to me that the differences between daytime and astrophotography include: 1) Dynamic range. Almost everything which interests us in an astrophoto is compressed into a tiny part of the histogram, so compressed as to be invisible in the linear image. This brings us to... 2) The 'decompressing' of the invisible data, known as stretching. This can be done in various ways to create different relationships between the brightness variations we are revealing by decompressing. We have a limited dynamic range available, so do we favour the very faint at the expense of local contrasts higher up the brightness range? Etc. Do we invert any brightnesses? (If we do, we should be sent to see the Headmaster. 😁) Which brings us to... 3) There are decisions to be made in AP stretching. Hooray! Different imagers will make different decisions and bring out different features. That's why, thank God, the one-click processing package will never be able to produce the best image. (There isn't a best one. They have different priorities.) 4) the daytime imager, using little or no stretching, has a much reduced problem with noise. 5) AP is done at infinity so the consequences, good and bad, of finite depth of field do not apply. 6) Multiple observers of the photographed daytime scene can see it and, largely, agree on what they've seen and how the photo relates to that. Nobody can see M33 as it is photographed, in any telescope. That's why we photograph it. I'll stop there...* *No I won't. 👹 I wish there was a one-click processing package for my astrophotos = I wish there was a one-stop word processing package which would write the perfect poem about the person I love. 😁lly

As has been said, apart from M31 and M33, galaxies make for very small targets. They are usually imaged at long focal length and high resolution - the hardest kind of astrophotography to do, both for the imager and the equipment. This means it's important to manage your expectations. With a small, lightweight setup you would get much better results on targets which are larger on the sky and are often stunningly beautiful. It would be worth thinking about this before making expensive decisions! Olly

Well, wow! 😁 I like the little reflection nebula as well. The only downside to the very hard stretch, in imaging, is that it can come at the expense of local contrast. In this case the Bat has a more 'filled in middle' than your softer stretch, as I remember it. Always a balancing act, of course. Olly

^^^ Great post and nice to hear praise for Photoshop, too. PI has some good tools but Photoshop remains an exquisite software package and should never be discounted. Olly