ONIKKINEN

I too dont quite understand the part about background extraction and removing of vignetting. Hard to say whats going on if the background has been extracted in your images already. I will say that SiriL background extraction will result in a blotchy image like yours if the sampler placement was bad or the flats didn't quite do their job, often both.

Can you attach a raw .FITS/.TIFF* file for people to have a look? One of each calibration frame (choose the flat randomly) and a light frame? Or just a calibrated light frame, that's better than nothing.

*Or .CR2 or whatever, since i just noticed its a Canon camera.

Quote

The comet in question is currently traveling toward Earth at 22,000 miles per hour. It’s hurtling inward from the edge of our solar system. Luckily, we won’t have to worry about the comet impacting the Earth. Astronomers say it will never pass closer than 1 billion miles from the Sun. That’s a little farther than the distance between the Earth and Saturn.

And it will happen in 2031. Doubt there will be anything to observe at this distance given that volatiles will still stay mostly frozen at the distance? Some dust tail probably but doubt it will be all that spectacular.

Would be cool to see an oort cloud resident closer up with some spacecraft though, but it might be too late for that kind of mission now.

My VX8 came with a non-round tube by design, secondary mirror with too short collimation screws (or the focuser drilled too low) to center the secondary under the focuser properly at all. The flimsy tube is not really a "mistake", its just light by design so cant fault it much, but the secondary mirror issue tells a sad story to me. It tells that nobody checked what they were doing to the tube and shipped it without knowing that the secondary mirror is literally impossible to collimate as it was sent. Obviously a fix to that cost me a few cents, but still it doesn't instill trust when something as simple as that mistake gets made.

I think mechanical stuff isn't their forte.

I do mobile astrophotography only so cant go back home and leave the scope unattended for long.

After setting up and the initial faff of collimation, guide calibration and the usual setting up i inspect the subs visually at first and see if focus needs touching and after it looks like the setup no longer needs babysitting ill do something else. I am not autofocusing so i need to keep an eye on focus for a while after starting the run because depending on the temperature difference the scope just went through i may need to refocus many times during the first hour or so when the long aluminium tube cools down and takes the scope out of focus with it. After everything is clear i always have a look with my 7x50 binoculars and see what i can find in the sky and if i get bored of that or its too cold, ill hop back into my car and either browse SGL or YouTube on my phone until I've had enough for the night. If shooting Lunar or planetary, then its obviously more hands on and there isn't much time to do anything other than handle the imaging. Sometimes i stack an image in the field when a few subs have arrived to see what im working with, especially if its a new target for me.

I think ill need a second scope, something as effortless as the binoculars preferably, to keep myself busy while the imaging rig is doing its thing.

Top right corner looks noticeably better than the others, so i would say you have collimation/tilt issues that need to be dealt with first before you can get the spacing right.

For my TS Maxfield corrector the spacing is not that important (i think ive read many newt coma correctors are also not that strict), i can be between 54 and 56mm and there is really no noticeable difference compared to tilt/collimation which is impossible to not notice in the corners. Your MPCC might be more strict with the spacing of course, but i would look towards fixing the mechanical problems first.

48 minutes ago, Wonderweb said:

Thanks for the info  I am currently using a 269c pro tec and, when I can get it to work , shoot at around 3 minutes which seems to be a pretty good exposure time with an idas d2 filter. Im pretty sure I could quite happily push this to twice that length if I needed to. My guiding is usually good and I dont suffer with elongated stars. They are just really soft. What sort of exposure lengths do you feel I would require to swamp the read noise with the ccd? Im usually in a bortle 5-6 area. 

Read this comment in a recent thread. Plug your own numbers in and see what you get.

With 8e of read noise you are looking at awfully long subs compared to lower noise cameras, but this might go in the nitpick gategory as people have used cameras like that for ages and the results are still great. But still its something to consider that shorter subs would ideally be avoided.

3 hours ago, Wonderweb said:

I appreciate there is a difference between mono and osc but from reading your final paragraph, am I to assume that the g2 8300 is better suited in pixel scale to the esprit 150 (1050mm fl) and will give a more pleasing  image (personal preference) than the imx571 (zwo2600mc) with its smaller pixels and cmos sensor? 

If this is the case then I feel alot of my questions regarding which way to go have been answered.  The moravian g2 8300 is well suited to my scope (orion optics ct8 - 900mm fl), will give me great results as seen with the m33 images and on astrobin, and is available at a very reasonable price second hand which is about a 3rd the cost of a new 2600mm. I have also discovered that it is still well supported by latest image capture software and, so long as I dont want to sell it and expect to recover anything like my original outlay, will serve me well for years to come. 

The sampling rate question is tricky to answer when one is OSC and one is mono. The mono camera samples as is, at 1.06'' per pixel with 55% peak QE, whereas the OSC camera samples at half the expected rate with 1/4th the expected QE (thats a way to think about it when comparing to mono), so at 7.52 micron pixels and maybe 20% peak QE whereas the mono camera is 5.4 micron and 55% peak QE. My point was that the comparison was not that fair or even to begin with. If you compared the IMX571 mono to the G2 8300 mono then the comparison would be a different thing entirely, but i would still bin the 571 in that case.

I image with a VX8 so the same kind of mirror as your CT8 and find that 1.84'' sampling is often oversampled, but my typical seeing conditions are poor and i have other issues in my system (bad coma corrector for example) that you might not have. For me the 1.24'' sampling rate the moravian would give would be definitely without a doubt oversampled most nights but from what i read this kind of resolution is a good target for an 8'' scope so i would be inclined to believe yes it is a good match for your scope.

If you find the G2 8300 for cheap, then its a good choice so not much more to say. Like you said one costs a toe and the other costs an arm and a leg so hardly a level playing field. Do keep in mind that with the higher read noise CCD camera you will need to expose much longer to swamp read noise well enough. It could be an issue with a newtonian and under dark skies, certainly would be for me at least.

25 minutes ago, Clarkey said:

FWIW I set up an AZ-EQ6 with a RC8 and guide scope each time I image so it is doable. The larger mount also tracks better than the HEQ5 - whether that is by luck or design is another matter. I would not really call a 6 class mount 'portable' though.

I too set up an AZ-EQ6 in the field in mobile astrophotography. I find it to be only marginally more trouble to carry than the EQM35, which is advertised as a mobile mount.

44 minutes ago, OK Apricot said:

I understand the idea that weight=bad, however, heavy as it is, isn't it the one time setting up on the tripod that it's weight becomes a "factor"? I've no issues with lifting weight or making appropriate transit storage in the van, so with that considered, for £300 more surely its worth getting the 6 over the 5? I'd be slightly in a dream world and lying if I said an SCT or large Mak wasn't an option in the future, which would be pushing the HEQ5. 

If you can carry the mount to your car then its portable enough so definitely go for the better mount if you can. I carry an 8'' newtonian, guiding and imaging gear, power supply gear, AZ-EQ6 + tripod weighing in at somewhere around 50-60kg to my car every time i want to do anything with any of my kit and its totally doable. Yes its a lot of kit and i take 2 trips to bring everything from my 6th floor apartment to my car and its a struggle every time, but i dont think the HEQ5 would be significantly less trouble for what is essentially only 5 minutes of huffing puffing and grunting per trip so saving for this reason is not wise.

13 hours ago, tomato said:

Just out of interest, here is a sort of (unscientific) side by side comparison of CCD vs CMOS, M33 taken with the same scope from the same location:

Esprit 150/Moravian G2-8300 mono LRGB 160 mins

Esprit 150/IMX 571 CMOS OSC 210 mins:

I actually prefer the CCD image…

 

Both are very beautiful, but i cant help but notice that the images have been processed differently (colour look clearly different, maybe the CMOS image could use some SCNR and maybe the CCD image went a bit too far with that? Cant tell exactly but they do look very different) and taken with vastly different specs clearly favouring the CCD in this case, so i dont think this comparison plays out very fairly.

The CCD image is taken with LRGB while the CMOS image is with an OSC camera. The CCD also has much larger pixels than the OSC camera, so i think its to be expected that the CCD image in this case would be better even if it had shorter integration? And yes, i do think the CCD image in this case looks better.

Your approach to starting AP seems sound to me, i think the choice of mount is a wise one. Better to go with a big mount and a small scope than the other way around, and one day you can upgrade the scope for something bigger and still have a good mount with that setup.

I would be wary of 2min subs unguided with the HEQ5 though, from what i am reading online i see the HEQ5 can have a 30'' peak to peak error over 480 seconds, meaning that 1'' trailing happens in 16 seconds. In reality the periodic error is not smooth and there are parts where shorter than 16s will have 1'' trailing too. In short, expect to either have trailed subs, or reject most of your 2min subs unguided. 30s subs are probably mostly solid and this is what i would start with. If you are imaging from light pollution then the 30s will be plenty long enough, if from darker skies then it will be less than ideal.

Guiding solves that issue, but i think its wise to start without guiding, if for just a little while. There is far too much to learn as it is with astrophotography so taking this in steps is a good idea IMO.

As for the flattener, yes you will want to have one. If you dont get one you will have significant field curvature and everything except the center of the image will appear trailed and out of focus. With the flattener you have to keep in mind what kind of backfocus is needed (depends on the flattener) and may need to buy extensions and adapters to reach the required backfocus with a DSLR. Remember though that a DSLR+T-ring will already eat around 55mm of backfocus. That is a good thing for the most part, since many correctors are designed for 55mm so if you get a flatterer like that there is no need to get extra spacers.

Actually, turned out half decent and maybe even presentable with a half-moon crop:

All the detail is in the terminator side anyway, so ill call this a planned end result. Not sure if the seeing supported the resolution here, but its not awful at least.

Missed some of it...

Ill try some trickery with some previous data to see if it can be turned into a full image. Probably not great but ill see it through.

On 14/04/2022 at 21:53, Richard_ said:

I'm able to introduce a lot more colour into the stars as before but the colour gradient of the stars caused by atmospheric dispersion are exaggerated with the Arcsinch stretch function so don't zoom in haha! I'll have to break the bad news to the missus that I'll need a mono camera to avoid this

Actually you can resample and the problem goes away. Unfortunately cant advice on how this goes with Pixinsight, but i would be shocked if there is no feature like this there. In DSS there is a simple "align colour channels" option which uses resampling and attempts to fix the colours and it works ok-ish. In SiriL, which i use, i do a bayer split for all the subs (dividing each sub to its 4 raw colour channels and stacking these as mono subs, which is the most "true" way to treat data from a colour sensor camera) and then stack those with one sub selected as the reference frame for all the subs. This stacking on one reference frame for all the different colour channels will align them during stacking and the atmospheric dispersion issue goes away.

That is of course if you dont want to buy a mono camera. If you do want a mono camera then best to tell the missus that there is no way to fix the issue without getting one 😉.

2 hours ago, vlaiv said:

Radius of coma free field is F^3/90 in mm

If you have F/4.4 telescope - then coma free field is ~0.9465mm (radius or about 1.893mm diameter).

That scope is rather fast and you really want to use barlow lens with it.

Critical sampling will be at about F/ratio = pixel_size * 4 (that is for 500nm wavelength - good value to use for full spectrum sampling).

You want to be at ~F/15 so you'll need at least x3 barlow if you want to go for critical sampling.

In any case - diameter of coma free field will be enlarged by barlow factor. x2 barlow will make it ~3.8mm. That is ~700x700 ROI with 3.8um pixel camera.

With x3 barlow - you'll be able to do ~1024x1024 ROI.

 

Ah my back of the napkin calculations where nowhere near correct then. Well i ended up using the 120MM since its mono and simpler to deal with. Not sure what strength of barlow i ended up with since i played around with the sensor to barlow distance but i think the 120MM is mostly free of noticeable coma, although seeing was not great and i doubt there will be a pretty picture in the end.

3 hours ago, ONIKKINEN said:

an ASI120MM that ill put in a barlow for this,

Actually scratch that, my Rising Cam has much higher framerates than the USB2.0 120MM mini with a reasonably sized ROI so i will be using that. Halved the amount of panels needed! That is if coma doesn't start to become an issue with a larger sensor but i think something like a 1600x1600 capture would still be ok-ish, maybe, hopefully (just guessing).

You can put these between the 2 parts being joined: https://www.firstlightoptics.com/adapters/astro-essentials-t-m42-adjustment-spacer-ring-set.html

That will prevent seizing for the most part. If you dont have enough thread to work with, or cant spare the added backfocus you can just lubricate the threads sparingly. I have a tiny dab of lithium grease on all my imaging train threads to prevent seizing and seems to work just fine and i have not destroyed any adapters since i started doing this. Obviously you shouldn't put so much there that it can spill over and start staining your sensor or some other optical component.

Nights are getting shorter here and i am desperate to try and do any kind of shooting while i still can but with the Moon in the way i am discouraged to try and get some sub par data for any of my running projects, so why not shoot the Moon? It will be low in the sky and my setup is hardly ideal for this but whatever a shot is a shot and ill take it.

I have an 8'' F4.4 newtonian and an ASI120MM that ill put in a barlow for this, but the question is: How to really shoot or plan the mosaic? Is there some software that can have a Lunar mosaic sequence saved in or is this usually just done eyeballed and manually slewed? I can of course just manually slew and eyeball the framing but would be convenient to have some kind of auto sequence to deal with the way too many panels that i would need to fill the entire Moon with. I am planning to take the shots with sharpcap as thats what im familiar with, but i have actually never used the 120MM for anything but guiding so far. I may take RGB with my risingcam through my coma corrector (at F4.2) to make a composite, but well see how the mosaicing goes first.

For me it was 4.2% import tariff from the UK. Not sure if this applies to Germany too, but i imagine it would if this is an EU thing.

Telescopes and other telescope related items all fall under the code 9005 and its subcategories. The code i would use for import is 9005 80 "other instruments" under the wider 9005 code: Binoculars, monoculars, other optical telescopes, and mountings therefor; other astronomical instruments and mountings therefor, but not including instruments for radio-astronomy :   (TN701)

https://ec.europa.eu/taxation_customs/dds2/taric/measures.jsp?Lang=en&SimDate=20220415&Area=GB&MeasType=&StartPub=&EndPub=&MeasText=&GoodsText=&op=&Taric=9005800000&search_text=goods&textSearch=&LangDescr=en&OrderNum=&Regulation=&measStartDat=&measEndDat=&DatePicker=15-04-2022

You can try to browse this impossible site to get the import codes, but you would have to put these into a German customs service or calculator to see if you will be charged the extra 4.2% or not, couldn't find this info easily.

Have bought from from FLO a couple of times post brexit and really not much to say, everything went smoothly on FLOs end and as smoothly as customs dealings can go on my end. DHL informed me when the package had arrived to customs and needed declaring and then i did this at the Finnish custom web declaring service, which while confusing and needs some updating to the current century is a minor headache at worst. I suspect its this way in many countries but for us we have to know the exact product code and search it on an impossible to browse catalogue of different products and if it goes wrong the package is held until someone checks it. Had this happen once many years ago (on a non astro purchase) and it was a huge pain in the backside to deal with. Thankfully everything astronomy related goes under "telescopes, their mounts, and their parts" so its somewhat easy with astronomy purchases.

I find that prices are very much comparable to EU retailers even with VAT and customs fees included so availability of stock is really the only thing that decides where my money goes in the end.

I wish @FLO had non VAT prices visible for foreign customers though. They do subtract VAT at checkout but i have to add the product to the shopping cart for the non-VAT price to be shown and it would be a nice quality of life update to just have an option somewhere where i can choose where im shopping from.

The EQM35 comes with 2 3,4kg counterweights whereas the EQ5 has 2 5kg ones so the real difference in mount weight is about 3kg.

Both have the same tripod so the extra weight is all in what counts the most: the mount head itself.

I would personally not recommend the EQM35 for anyone, for any use, with any size of scope. Sure, i think it can be used for visual with relative ease up to the hallucinated advertised limit of 10kg but i really dont see why anyone would, considering the EQ5 is just around the corner in terms of price, and has more or less the same weight if given equal counterweights so the mobility point flies out the window with it.

For imaging, it will be nothing but trouble if you try to get anywhere close to the weight limit. I would not buy the mount if an imaging resolution of greater than 3'' per pixel is in mind. But the comment above stating up to 2'' RMS guiding error is reasonable to expect from the mount. But do keep in mind that this is a show-stopper amount of error even in lower resolution imaging setups that will mask most of the small details that would otherwise be captureable. Below is my typical guiding performance. Notice the aggressive RA periodic error that guiding is not able to flatten out because the mount is mechanically fighting against itself with guide corrections (the sawtooth thing). Also, hilariously declination has a periodic error too even when it is not being guided at all. This is just normal behavious because of the McDonalds toy quality innards flopping around how they please.

Now why am i saying this? The EQM35 has no bearings in it what so ever. The design is inherently flawed and there is no amount of relubrication and cleaning that will make the mount run reliably time after time because the innards are supported by plastic and paper washers and poor quality lube. If you replace the lube with better stuff, like a lithium based grease you will find that the mount actually has more backlash and wiggle in it because the thick stuff Skywatcher puts there eats part of the backlash away and just hides it. The declination axis is the same as in the EQ3, which most call junk. There is no way to get rid of the backlash and even if you could it would not be consistent and guidable reliably time after time. For best use case you would either guide in one direction, or not guide at all in DEC (i had to do this). The RA axis is decent though as it is a bit improved over the EQ3, but it still does not have bearings so its not reasonable to assume it will perform reliably.

The EQ5 has bearings in both axis and its not so much of a hallucination to try to put closer to the limit of 10kg on it from what i read. For a difference of almost nothing at all in price, it really does not make any sense to get the EQM35...

All of the above is personal experience and opinion but i was once like you, looking for a mount that looked convenient to me and ended up buying what i believe to be a borderline scam built to just be "the first mount" which you then sell and replace with a functioning mount later (and line Skywatchers pockets with more money). Take with a mountain of salt, since i am very salty about this mount but none if the above is a lie! Dont buy it, you will regret it one day!

On 07/04/2022 at 21:13, vlaiv said:

Why do you think you'll tweak that advice?

You think that above image is well sampled at 0.39"/px - although it is presented at 0.5"/px and has FWHM of 1.9"?

One of two images below has been reduced to 50% in size and then resized back to match the original. Which means it was sampled at 1"/px at that point. If detail is there in the image that needs higher sampling rate than 1"/px - then that detail should suffer. Can you tell which one of two images was resized to 1"/px and then up scaled back to original size? (Actually you should be able to tell as it has less noise, but all the detail is still there).

@Magnum

I dont understand any of the in depth stuff discussed here so probably shouldnt chime in, but i simply cannot tell the difference between these 2 images so what about this then, because if you actually had detail at 0.5" it would have been lost at resampling to 1" and back?

I tried this too by resampling your posted jpeg back and forth and no really cant tell the difference in detail.

3 hours ago, osbourne one-nil said:

That's exactly how I feel - so I'm not completely mad to think that way!

My only reservation is on windy nights, the small refractor will be less burdensome on the mount, but I can probably create some sort of semi-permeable wind-break if I wanted anyway. 

I imagine summer is a frustrating time for you...you must be further north than me! 

Ah, well the wind thing is true. Too much wind and its better to give up than bitterly try and salvage part of the night which i assume to be a lesser problem with small fracs.

The 21-22 astronomy season has basically ended by now as there are no moonless nights before the last astro darkness ends next week and after that, 4 months+ of break.

46 minutes ago, barbulo said:

I believe cloudy nights have a good share of guilt when it comes to spending money. Agree?

Looking at the past season i have somewhere around 20 sessions with the scope. Im not going to even try to calculate how much €€ that is per night...

I dont have a small scope, nor do i have a desire to get one. I do darksite (often without the dark lol) imaging only so time under the stars is very limited and building up a long integration with a small aperture scope is not what im looking for. My 8'' newt is big enough that brighter targets are 1 night projects if the skies are decent enough, which is not what would be the case with a smaller scope. If i wanted to image an extended target that doesn't fit my field of view, i could just mosaic and bin more so i dont really see any downsides to having a bigger scope.

13 hours ago, Richard_ said:

Please do share any images you create if you decide to continue playing with my data. Thanks for taking the time to provide good feedback too, it's much appreciated 😊

I did do this as a quick process to see the star colour issue first hand:

I binned it 2x2 in ASTAP, but it could be binned more without much or any loss of detail, not that i focused much on detail in this shot (mostly colour processing). 5-6'' fwhm stars will do that to an image. Not much you can do about the seeing other than try to only shoot near zenith, but that's not always possible of course.

Thats getting close to the limit of where the atmospheric dispersion effects start being noticeable at a glance, but there is nice variation in star colours already so its saturated enough IMO. I started stretching with an asinh stretch with a power of 1000 in Siril. Dont quite know how this works but the asinh stretch also stretches colours and the resulting image needs less, or no saturation afterwards. The regular histogram stretch function usually results in an image that needs a fair bit of saturating afterwards to get anything out of stars.

The data is quite nice, apart from the big stars. Would love to see this with more of the good stuff and the seeing effected subs removed from play, weather willing of course.