pipnina

Unfortunately all is not well. Some issues remain with the scope, maybe it has even worsened as there is now a notable amount of colour at the corners! I got the chance to give it a test last night. Of course having not had the opportunity to til now, I sent her to look at M42! Aside from my constant amazement whenever I image this target at how little exposure is necessary for a clean image (in this case, 6 minutes!), I am rather disappointed to learn that this endeavour of sending the scope off for service has largely been in vain. I wouldn't say useless as I need to investigate further, and Mr Reid did affix my focuser which I did not attach properly the first time, as well as clean some "mist" from the fluor element. But coma is still present, and maybe pinching (looking at Hatsya, that halo's points seem a bit odd, I don't notice it anywhere else and to be honest, that effect doesn't bother me much). And worst of all chromatic aberration at the corners! I am not sure if this could mean the lenses are misfigured, or if I now have an issue where the corrector at the other end is just not up to task. I have always meant to replace it with a higher quality one but maybe this is the time? I don't know. But if we assume Mr Reid's work stayed in place in transit, the problem must lie elsewhere! Keen to hear anyone's thoughts on this 😬

Why stop there? https://www.astrosysteme.com/en-us/products/az2500-f6-f2/ Anyone got 7 million euros to spare?

The retail pages say it is threaded for 2" filters, which use M48 thread. You can see the thread on the camera side is smaller than the barrel on the focuser side, so the camera side thread is almost certainly M42x0.75mm (T2) You can see in this thread a version with M48 connection on the camera side, and see how much bigger the thread on the camera side looks compared to the same 2" focuser barrel. Hope this helps

I think lasers can't collimate cassegrain telescopes fully, as your beam goes from focuser to secondary, then when the secondary is properly collimated the beam comes back to your laser source. I.e. you get no reflection onto the primary. I think there are multi-beam tools that let you collimate cassegrain telescopes with a focuser-mounted tool, like this one: https://www.teleskop-express.de/shop/product_info.php/info/p11188_TS-Optics-2--LED-Collimator-for-RC-Telescopes-and-all-other-Types-of-Telescopes.html But like you I have little experience collimating a cassegrain scope, so I can only offer up the little knowledge I have... This might be some help, even though a CC and an RC are a bit different:

Looks good! Did you use the Astronomik UV-L3 cut trick with your FMA180 or are you shooting it "full spectrum"? Trying to work out if this little thing is going to satisfy me or if I will want to save up for something like the ACL200 or Borg 55FL

For my 571, the hot pixels are there but get removed by the default settings in pixinsight. I do dither though on every 3rd sub. I also found that for my much noisier Nikon D3200 which had super bright hot pixels, that the hot pixels would overpower the signal even when dithering and the hot pixels would trail all over my images. However the ultimate savior for me was the Sigma-clipping stacking method. It does a phenominal job of removing hot pixels if you dither your subs. Here is the rejection map for a 1.5 hour stack of 17 second exposures taken on my google Pixel6 on the main camera, when using sigma clipping in pixinsight. My goodness! And the final stack, once I finished processing... Those hot pixels are gone! Ok, the image isn't exactly "clean", but we are dealing with a very tiny and poor quality sensor, plus optics that have a very complicated distortion and abberation pattern which makes it impossible to work with in a desirable way for astro. But if sigma clipping can make a phone produce an image this good and remove all that gunk from it, it should work just as beautifully on a much higher quality astrocam!

The colour in those stars is gorgeous!

I agree it looks like the IR light on the phone reflecting off of the eyepiece. Like Elp says you can probably stick something over the IR bulb (use online diagrams to find it, it's quite well hidden from the eye on my phone). I'd say you should experiment with your current gear and consider upgrading only when you feel confident that it's the right next step, after you've tried things like stacking phone videos on planets etc. Good luck!

The telescope has made it home! Es said he cleaned the lenses, identified the middle element as a "fluor crown" and said it had a slight mistiness to it, but he has attempted to clean it up. He also epoxied the focuser to the tube so it should now be nice and rigidly attached, unlike when i sent it to him. Sadly the weather tonight is poor and the forecast doesn't show much hope either, but I hope to test it soon! I actually thought he was underselling himself a bit when he gave me the bill, but as long as he's happily compensated and i haven't broken my bank all is well I suppose. Fingers crossed!

I don't know about eyepieces, but when i took up the option for lens thinning years ago my vision was plagued by chromatic abberation even slightly off center. Never taken that option since despite my Professor Farnsworth thick lenses.

I love the redder tone in the bottom one! I feel like if you could somehow combine the rich orange in the bottom with the slightly deeper blue of the top image it you'd have the best of both! Amazing!

I realised i forgot to link the corrector I found before: https://www.teleskop-express.de/shop/product_info.php/language/en/info/p14460_Starizona-Nexus-0-75x-Newtonian-Focal-Reducer---Coma-Corrector.html As I stated... it is not cheap! And only advertises correction to slightly shy of APS-C format (28mm circle, compared to diagonal of most APS-C sensors around 31mm). The example images look good, but aren't very high res and look like they might use some starless processing? hard to say. This is so far the only coma corrector to offer more than just a little bit (i.e. more than 0.95x) reduction.

Seems I've unintentionally paper bombed his workshop 😅 I used (per recommendation of a local store) printer paper scrunched up to cushion the bottom of the box, and the other end was cushioned with bubble wrap... And I forgot to mark which end was which! Plus, my botch job at affixing the focuser to the tube has failed on him as he lifted it from the box... Oh dear. I have apologised but he did say it made him laugh so there's that. On the plus side early impressions of the optics are promising!

The scope is now in the hands of Es, awaiting prognosis! I had to find a new post office as the one most local to me has closed down as if jan 1st, in the end postage via parcel force 48 came to £72! DHL didn't charge that much, but it's Es' preferred courier so I figure he trusts them for a reason (well he said Post office, but I think royal mail doesn't deal with items this size, leaving PF as the only other option). But I also don't know if DHL was told the sale value of the parcel when it was sent to me. Maybe I could have sent it cheaper if I undervalued the parcel (I used the value I bought the scope for) but even though glass isn't insured, I'd be devastated if the parcel was lost entirely while undervalued by the courier. At any rate, fingers crossed!

Sadly I think it's true. While I wish this not to be misconstrued, I do believe humans have managed to violently overpopulate and we would have been better off ecologically plateauing about 5BN people ago, which lines up roughly with what our planet could have provided for us without the use of fertilisers (originally bird poo scooped from islands and mined in a manner most irresponsible which would have led to the famine of billions if not for the discovery of synthesized fertilisers prior to WW1). We consume food in volumes that could never exist via "natural" means, much of which is grown on land claimed from ecosystems that are destroyed for farming, and then is fed to livestock (98KG of grain turns into 1KG of beef). We package everything, and make so many of our daily materials out of stuff we cannot dispose of. Plastic recycling is little more than a fantasy as almost all plastics go un-recycled and end up burned or in landfill eventually (many poor nations are effectively poisoned as richer nations pay them to take their plastic waste, those nations then have little choice but to burn it, which releases extremely toxic chemicals). Even PLA, which is made of corn starches, cannot be biodegraded as advertised in nature, it requires enzymes that are artificial and high temperatures. Plus, every PLA on the market is packed with additives or is even an "alloy" with other plastics which mean recycling and complete composting cannot happen in many cases, leaving us with incineration as the only option for proper disposal. Air travel (which still uses lead additive fuel) allows us to visit places en masse, and ruin them just as fast. I would very much like to travel and meet my distant friends, but it's hard to compare my feelings and desire to see other lands to the damage I would/could cause in collaboration with everyone else doing the same. I think this is only the tip of the iceberg for what we do to this planet, and ultimately ourselves. Plunder now, regret... Sometime in the future. I have developed a lot of anxiety around my own environmental impact. Near enough everything I buy or throw away gives me this inkling of guilt, but it's not like I can just... Stop living? If I didn't buy things that would eventually turn into waste, I'd just sit here like a lemon for my whole life, never enjoying anything, as all my hobbies cause some kind of unspeakable damage, and I'm not much one for reading and gardening is something you can only do so much of in a day, if you have a garden. I apologize for being so morbid but it's what weighs on me whenever ecological / environmental happenings get discussed 😕

I have only done research on this myself, but reducer coma correctors seem extremely rare, and when you find one, it's expensive! (Think £500+!) I found them with 0.75x mag, and they all claimed to be suitable up to APSC, but then the 4element GPU corrector claimed to be full frame suitable, and I don't think it was based on my own experience. From what I understand, parabolic mirrors are great if you plan on using them plain with eyepieces etc, but awful if you want to correct the peripheral field as well. This is because coma correctors end up creating some spherical abberation (like the Baader) at the center as a result of the parabolic mirror being perfectly corrected for sphere already. But if you paired the Baader mpcc with a hyperbolic mirror (somewhere around k=1.22 according to people on cloudy nights) the center would be corrected for sphere as well as reasonably corrected at the edges. I can see if I can find the correctors when I get home and drop you the links. For now though I might say it's a bit "untested" as I struggled to find high Res example images, let alone raw subs! Best of luck with your new kit!

I actually sold my sigma 105 f2.8 macro last year after I got rid of my DSLR. It did handle quite well but star shapes weren't exactly ideal at the corners, and that was on an aps-c sensor, and the lens is supposed to be full frame suitable. It was very good at normal photographs though, I definitely got my money's worth from it. This capture is very nice too, beats a lot of stuff I captured with mine for sure. Shows what happens when it ends up in the hands of someone capable ha. I looked at the art lenses, as well as the Zeiss lineup when looking for imaging lenses in the 1-200mm focal length range... Sadly while all very well corrected for distortion and chroma, ALL of the fast lenses have insanely high vignetting (most of the f1.4 lenses are only 30% illuminated at best by the corner of a full frame sensor) and the MTF curve is very dodgy. Plus they cost as much as or more than a redcat51 or askar ACL 200. I'm sure I'd adore those lenses for regular photography, but my mind does so much more pixel peeping with astro!

This might explain why my dad and I were struggling to see it, stellarium on mobile has it as mag 5.8, I was struggling to see the comet but mag 8, 9 stars were easy in my 10x50s tonight.

Also, you aren't following the topic - heads up

The only idea I have is to set the telescope up during a cloudy night, point it at a bright torch of some sort (could make a pinhole in a foil sheet to simulate a star maybe), and move the bright light source around the field of view of the scope, even out of field, and see if the reflection pops up. When you find it, be meticulous in working out where it's coming from. Remove the corrector and see if it's still there, then try the filter wheel, oag, even take the cam off entirely and see if it's also there in an eyepiece. Looking at where the focal point of that curve would land, way off screen, the only bright object in that area is mars... Does it show up in the field if mars is near by? It's brighter than any star by a long margin so if anything can cause a reflection in an otherwise dark sky that might be it.

The tipping point was probably that my 50mm/f4 finder was mounted on a 30cm dovetail on the top of the tube rings, about as far away as it could possibly be. This was to get it off of the tube itself as I suspected it was causing flexure when guiding. Plus I had a losmandy dovetail on the main scope which was heavier and a big flexible dew shield on the front of the scope to try and cut out some of those off-axis reflections. quite possible I simply added more accessories to mine / further away etc. The newt wasn't far off balance though, a piece of string with my star adventurer's 1kg weight on it hanging off the counterweight bar mostly fixed it.

Both my 8" F4 newt and 130mm f6.6 triplet are impossible to balance on my HEQ5. the 10KG of counterweights is simply not enough for either of them. I still get sub-arcsecond guiding (typical between 0.5-0.8RMS total) with both, but the refractor is definitely more stable with fewer wobbles, probably on account of having a lesser wind profile. I have wanted a mount upgrade for a while, but the market seems to be moving a fair bit at the moment and the choice is not as clear cut as i think it was when I bought the HEQ5 in 2017, many more options in the £1500-4000 price range than just stepping up to a higher tier skywatcher mount.

I can't remember where, so I don't know how accurately my memory serves, but I think I read/heard that areas in the lake district do their absolute best to keep tourists on specific paths so the sheer volume of people doesn't destroy the very thing they've come to see. We closed off stone henge with a fence because people kept vandalising it We can no longer enter the prehistoric caves with the paintings in france (discovered during WW2) because the presence of moisture from human breath and artificial lighting caused plants/moss etc to grow on the walls, slowly destroying the paintings so that we could view them. So they built a replica "next door" and closed off the original to everyone except scientists. Look at any major tourist / package holiday city before and after the rise of the aeroplane, the effect of the tourism industry is almost always unintentionally destructive. Best we can do is keep our own impact to a minimum when we visit, and for affected areas to impose limits and controls to preserve what makes them special. Most of these places only exist as they are once!

I can't attest to photoshop's needs, but as a Pixinsight user I find RAM quantity, drive speed and multi-core CPU performance to be very important. Some stacks I've done (where about 800 24MP subs were used) have literally consumed all 96GB of ram in my system and then started to eat into my 50GB swap on my SSD too. But Pixinsight's process is insanely poor performance compared to alternative stackers. It also takes up a lot of disk bandwidth and IOPS (in-out operations per second) so my SATA3 SSD only just keeps up. I use a Ryzen 5800X but given as the 5950x is faster in every way and also about the price I paid for my 5800x at launch these days... That might be the CPU to get as the new gen 7000s are a bit pricy for a slightly underwhelming gain I hear.

So if I wanted the ground to be properly exposed, I should get a meter reading with the center of the frame pointed at the ground, then frame my shot? Works for me if that's the case, I was probably exposing for the sky.