ONIKKINEN

You will not be able to get focus on anything without enough backspacing. So either the diagonal or an extension piece in place of the diagonal. Would be better to ditch the diagonal and get the extender, as a poor quality diagonal is just an extra source of optical aberrations that is really not needed.

Or put the camera in the diagonal, actually? Not sure if the focuser in the ST102 likes to have a diagonal and a camera attached to it though, but you could try to see if there is an image.

The eyepiece wont reach focus either without the diagonal. Refractors have long backfocus distances behind the scope to give enough room for the diagonal so now without one there is no hope of reaching focus without extensions. You will need an extension that is the same length as your diagonals light path, now what that length is i dont know (since i dont have this scope) but you could try to measure it roughly and get one that is closest to that. I think it should be somewhere around 100mm? But do check this yourself before buying something.

Now that its not saturated it doesn't matter nearly as much anymore, if there was detail it would be visible here. You can see your exposure is usable now as none of the histogram peaks are to the right edge (saturated). If you dont see any difference when rolling the focuser in and out you are probably far out of the focal plane and so this difference is difficult to see. How is the camera attached? If its attached at the same place as an eyepiece, it should reach focus at roughly the same place as that eyepiece. If you have taken the diagonal off, you will need to have some kind of extension between the focuser and your camera to replace the lost light path of the diagonal.

Looking at your settings its difficult to tell whether you would be in focus or not. You have a tiny little area on the sensor ROI active so the field of view here is much tighter than you think. You are also over-exposing quite a lot. Green peak is oversaturated. Use the full sensor and drop your exposuretime until you get a proper exposure and it will be easier to tell whats going on. And the green colour cast is to be expected, since you are using a camera that has twice the number of green pixels compared to red and blue so dont worry about it.

I am doing some window shopping and saw this: https://eu.primalucelab.com/equatorial/skywatcher-star-adventurer-gti-mount.html . No price available right now. Quoted as: Available starting summer 2022. Looks like it might have the AZ-GTI style tripod based on the picture. Perhaps its aimed at replacing both the star adventurer and the AZ-GTI as it does what both do, but better? Probably wont replace them though as this one has to be pricier than either of those.

Well i did that and now FWHM is smaller in the split version compared to the RCD+BIN2 version. Curiously noise in standard deviation is lower in the RCD+BIN version, but in the RMSE (whatever this means) its the other way around. Interestingly noise measurements of both kind are much higher than with pixel area relation, so this means you are right and some kind of blurring (acting as denoising) could take place when not wanted? RCD debayer + BIN2: Full Width Half Maximum: FWHMx=3.83" FWHMy=3.50" RMSE: RMSE=5.721e-04 02:06:39: Background noise value (channel: #0): 2.896 (4.419e-05) 02:06:39: Background noise value (channel: #1): 3.270 (4.990e-05) 02:06:39: Background noise value (channel: #2): 2.845 (4.342e-05) ------------------------------------ Bayer split: Full Width Half Maximum: FWHMx=3.71" FWHMy=3.50" RMSE: RMSE=5.690e-04 01:57:23: Background noise value (channel: #0): 4.011 (6.120e-05) 01:57:23: Background noise value (channel: #1): 3.725 (5.683e-05) 01:57:23: Background noise value (channel: #2): 3.691 (5.633e-05) ------------------------------------- This time AstroimageJ reports both as 2.60 pixels in FWHM, which is close enough to SiriL measurements. I avoided Lanczos-4 before because it left some cold pixel artifacts around some stars, but ill just deal with this with cosmetic correction or something since a drop of 1'' in FWHM is pretty significant.

I measured FWHM using the SiriL photometry tool. Have not tested whether or not i can spot the difference visually so not sure if the difference matters, or not actually sure how to do an apples to apples direct comparison in terms of stretching equally. Both images were from the same 120 calibrated subs, just went through different routes to get to the final RGB image. I am pretty sure i used the default interpolation method for registering: Pixel area relation. But here is what i found using the SiriL photometry tool around a star and running the "noise estimation" tool in SiriL (i think its just standard deviation): RCD interpolated, then binned 2x2 in ASTAP: Full Width Half Maximum: FWHMx=3.87" FWHMy=3.68" RMSE: RMSE=5.577e-04 17:06:50: Background noise value (channel: #0): 2.416 (3.687e-05) 17:06:50: Background noise value (channel: #1): 2.764 (4.217e-05) 17:06:50: Background noise value (channel: #2): 2.363 (3.605e-05) -------------------------------------- Bayer split, then recomposited as RGB: Full Width Half Maximum: FWHMx=4.89" FWHMy=4.65" RMSE: RMSE=2.526e-04 19:24:44: Background noise value (channel: #0): 1.351 (2.062e-05) 19:24:44: Background noise value (channel: #1): 1.555 (2.372e-05) 19:24:44: Background noise value (channel: #2): 2.441 (3.725e-05) Running the multi-aperture thing in AstroimageJ around the same star i used in SiriL gives me: RCD and bin: FWHM 2.64px Bayer split: FWHM 2.91px Again there is a difference in size but this time the difference is less severe. There is also a difference in brightness, apparently. Wonder what went wrong 😬. I was going to make a thread investigating different binning and resampling methods for OSC and how they differ, but i realized i dont understand the data i got from my tests. I understand some points, like star size and background noise, but i dont understand why they would be so different so just kind of forgot about it.

I did run some tests on SNR and star fwhm but got some results i cant explain. The splitstacked image had the best SNR, but worse star sizes compared to stacking with RCD interpolation and then binning the stack 2x2. Not sure why that is, maybe theres someone who could answer that but its not me. Hopefully i remember this right but ill have to check the data i got when i get home. Ill post what i found in a few hours, if i ever get off work that is.

You can use the "seqsplit_CFA" command to create split frames from the loaded sequence subs. Only works if the channels are still intact and debayering has not taken place. For a 100 subs you will get 100 subs each with the prefixes CFA_0 to CFA_3, so 400 subs. 2 of these will be green, 1 blue and 1 red, you have to figure out which number is which yourself but for me CFA_0 and CFA_3 are green, 1 is red and 2 is blue. I have a script for SiriL that calibrates my data and then outputs split monochrome frames. Takes a few minutes to run on a batch of a few hundred subs. Subsequent stacking is much faster since its now mono data and 1/4th the size in megapixels per frame.

Whatsapp also is guilty of gutting images sent through it, which is why sending it as a link to somewhere its already posted or attaching it as a file is the way to go. I tried to compress images myself to see if there is a point where whatsapp agrees to send it as is but as far as i know there is none and the image always goes through some rough cuts. I find this pretty funny as i do some of this (not the hill, but 6th floor and elevator is kinda dangerous) when i escape TO a B6 or 5 zone from where i live 😀. You get used to it. Or do i just tell that to myself? Who knows.

Agreed, too many variables in play to point towards a clear problem. Ill see what i can find from the hardware store to beef up my current kit somehow. Rather not spend a fortune on this right now.

Does not. Smoothbore 2'' barrel, fits the focuser very snugly.

Im gonna be honest and say that i was a few cans too deep into a case of beer at the time of posting and im not sure what my point was or if there even was one, other than tilts exists somewhere in the system 😅. Im sure there was a train of thought going through my mind when posting but i couldn't tell you what that was now. Connections are threaded as far as they can be, with a 3-point compression ring connection between the CC body and the focuser, which is a Baader diamond steeltrack. I dont see a difference in apparent collimation with removing the collimator and placing it back in, trying to find out if the connection is sloppy. If i understand my own post right, i made the conclusion that the CC would be somehow to blame, but since it moves with the camera when rotating the imaging train, the tilt should travel with it as well. And seeing as the bad corner has traveled 90 and not stayed in the top left corner of the sensor, the tilt is something before the imaging train (collimation). Of course its possible the CC is miscollimated too and i would have to collimate trough it to get the best result, but i think most of the tilt is in collimation. I did a little test by punching the OTA (lightly) with a laser attached to the CC and it did move a bit every time, erratically. The OTA itself is very thin and soft aluminium in the VX8, so i have reason to believe that might be part of the issue. The effect is most apparent in stretched and rainbow rendered flats below: In this view reds represent the brightest pixels and purples the coldest. The bright spot doesn't stay in the same spot over the sensor when the imaging train is rotated so id say its just my collimation is out of whack.

Picture 1 is at 90 degree orientation, picture 2 at 0. Both images are from different sessions, and so have different collimations, although both are collimated via the same method to the best of my ability using a cheap 1.25 inch laser collimator (that i have collimated myself) NOT through the coma corrector, but i am 100% certain it was "right" on both cases. in the first issue the tilt is to the top left of the frame, on the second image that is rotated 90 degrees to the left it is to the bottom left, as i would expect if it was not sensor related. Rotating the camera involves me rotating the entire imaging train, which consists of a filter, the coma corrector, some adapters, and the camera. Am i right in saying that the tilt in my system is located in some place other than the sensor using the above information? I feel like this is a simple question and i should know the answer, but im no expert and am proven wrong left and right. If the tilt is not in the imaging train, it must be in the scope am i right? That leaves just collimation with my newtonian as the culprit. But here is the issue, i have my imaging train intact when using my scope, so i collimate without the coma corrector. I have a 2'' to 1.25'' adapter where i put my trued cheap laser into and i confirm the colimation each time i use the scope (because all of my imaging is at darksites, so bumpy roads etc will guarantee the scopes needs checking). I think this is due to my coma corrector itself being miscollimated? Sounds reasonable? Just guessing. I cant be certain because it involves removing equipment but im pretty sure i have different collimations with the CC and without. Easy solution: Collimate through the coma corrector. This step is not what i want to do as it has me unscrewing and screwing out equipment each time i want to use my scope. Rather have a solution without. ??-difficulty solution: Try to un-mess the CC alignment, if it is even possible. Or some other method. Feel free to suggest if you have one in mind.

Thanks for the feedback. I think applying just the right amount of saturation before things get "crunchy" is key to get different star colours nicely balanced. I think the diffraction spikes of my newtonian also work with me in this, nicely spreading out the colours where applicable.

60x30s exposures with my VX8 and Rising cam IMX571OSC, binned 2x2. Took this while waiting for my main target Abell 1656 (coma cluster) to rise above a treeline, but that data ended up being quite cursed for a multitude of reasons so time will tell if that picture ever gets finished, but probably not this year. I like the contrast of different star types in this cluster, the bright blue (stellar blue that is) B-type stars, and the few noticeably differently coloured A, F and G-type whiter stars along with the few M-type stars that have made it to the end of their lives and will soon blow up or wither away as white dwarfs.

Have a go with starnet++V2, would be relatively simple to process the galaxies, stars and IFN separately with some layer trickery. I would be happy with the capture itself though since IFN is such a pain to capture with a reasonable integration. So maybe some tweaks but the picture still looks good.

Quick look at the Moon with my 7x50 Nikon Aculon binoculars. Always surprising how much the little binos can show of the Moon with so little magnification. Plenty of craters and little nooks and crannies around the terminator. Of course looked at the other bino targets too: Pleiades, double cluster, Orion, smudge of M31 close to setting. Cant find other galaxies with the Moon still up. Will wait and see if skies are still open once the Moon sets.

I hear you. This is what 100% clear skies look like according to clear outside, good to stargaze, windy.com and others: Ah well gotta use what we can when we can. Would go even crazier if i only used the actual clear nights...

The Astronomy.tools CCD calculator is hardly helpful with what it considers good sampling rate for a given system. Its best to think of the higher estimate as the better choice than the lower one. For example the higher estimate of 2'' per pixel is perfectly fine for my 8'' scope, but the lower estimate of 0.67'' is without a shadow of a doubt oversampled. I would have to live on a mountaintop, or a desert, or better yet a desert mountaintop to be able to sample at this rate and not oversample. Guiding would also have to be epic for this to work. By binning 2x2 you get a very reasonable resolution with your scope and camera combo. But for the mount question i think the EQ6 would do just fine with the 200PDS. I have an AZEQ6 and have no major complaints with my 8'' F4.5 newt. It can be a little bit windy and will work just fine, but if there are sudden strong gusts it can still be problematic, but that's just how it is with long scopes, especially newtonians. So far i have gotten 0.7'' and 0.65'' RMS guiding in mild wind and less than great seeing with mine guided by a 60mm F4 guidescope.

Whether the L-pro is worth it depends on a few things IMO. Level of light pollution and type of target you have in mind. Also, whether you want to have a real colour result in the end, or make it easier for yourself to get one. Using a light pollution filter will make it very difficult (impossible for most) to get a real colour result in the end because you have blocked a part of the visible spectrum during capture. If your sky conditions are very bad, like lets say bortle 8 inner city skies then yes you may want to use one, but in conditions better than this maybe not and even in these conditions also maybe not. Broadband targets, like galaxies benefit very little or not at all from a filter like the L-pro, because light pollution and galaxy light shares the same spectrum so by blocking light pollution you also block starlight coming from the galaxy. For emission nebulae it would work just fine, because emission nebulae have 2 major emission lines that produce most of the signal imagers are interested in: Oxygen 3 and Hydrogen alpha. Neither are effected by the L-pro and here there are only positives when using one. But for emission nebulae there exist much better filters than the L-pro, like the L-enhance and the L-extreme. So personally i would not be using the L-pro in pretty much any situation. When imaging galaxies, better without, when imaging emission nebulae, better with another filter. Perhaps its best to start without the filter as its not really necessary or wanted for some cases. For the 550D you will probably want to install the 3rd party firmware package called "Magic lantern" https://magiclantern.fm . It expands the Canon limitations for many parts and unlocks features such as an intervalometer, improved focus detection (works actually decently for astro too), more freedom on shutter and ISO settings, more video shooting modes (if you want to do planetary/Lunar). Do keep in mind though that its still 3rd party and something might go wrong. I personally had a few hard crashes where i needed to reset the software. These happened when playing around video capture FPS which the firmware warns you about so not unexpected.

To be honest im still looking for decent spots myself... The Helsinki light dome extends much further out than one would expect from its population. There is one reasonably close spot with decent skies in Porkkalanniemi to the southwest of Helsinki. Its barely outside the light dome and every direction except north east is decent with bortle 4 skies. The place is often quite windy though and requires a sturdy mount to make imaging possible. For skies better than this im not sure which direction i would drive. Probably north a couple of hours, but no such places that i have found closer than this kind of drive away. You can check Finnish stargazing spots looking at this map: https://www.taivaanvahti.fi/locations/browse/map Porkkalanniemi is the lone spot to the south of Kirkkonummi on the map. Accessible by car (its a parking lot) and not too far away. There can be some traffic during normal waking hours, but usually after midnight its quiet. Some folks also know its a stargazing spot and turn of their car headlights once they get close and see there is a guy with a scope.

I have only had a handful of experiences with other people whilst out with my scope and most of them dont care or know what im doing. Most also dont approach and just sort of glimpse from a distance for a few seconds before moving on, but i think that's a Finnish personality issue rather than a hobby issue 😅. This one lady stopped by with her car once and asked if there is a good place nearby to try and image the northern lights from (was forecasted that night) and asked what i was doing and i just answered oh im imaging this pair of galaxies in Ursa major (M81-M82) and pointed upwards to where it is. I would have loved to explain everything because talking astronomy with strangers is such a rarity, but she just sort of looked at me confused and didn't say anything? She then just said oh well thanks for the help and drove off to where i recommended a better place would be. The one time a person has actually come to talk more about what im doing was pretty nice though. They were curious as to what im doing and asked what the giant tube is and how it works (newtonian). They were surprised to see that you dont look through it from the behind and generally didn't seem to understand how the scope works. Newtonians look really strange to people who are not in the hobby it seems, but anyway ended up looking at the Moon at 200x while it was setting. Wasn't the best view i have had, but im pretty sure it was the best view this guy had seen. Friends and family also dont seem to care or understand that much. If i show some half-acquaintance from work what i have imaged 50% of the time they just straight up dont believe me and think its impossible to image these things without NASA equipment. This hobby really is quite niche and underground it seems.

I like the legacy sky survey viewer: https://www.legacysurvey.org/viewer It has many different catalogues to choose from like several optical surveys, some IR, some H-alpha, some dustmaps etc. Hunting IFN imaging targets with this is a piece of cake.