rnobleeddy

Thanks for the detailed reply! What's more, it makes sense. My mistake was assuming the thing I'm imaging had a signal far above the background sky - of course, that's because of what I see in the final stretched image, but I'd do better to assume it's the same level as the background sky for these purposes.

Perhaps if you stick with OSC this is partially true. I've certainly got good images from my DSLR with sufficient integration time. On the flip side, at least the Canon 450D/550D I've used tend to have noise that makes it to the final image if you don't have sufficient integration time and don't perform large dithers every sub. I imagine newer sensors are better, but then they're more comparable in price. For example, the Canon EOS Ra costs £2500 so it firmly in the same range premium cooled astro cameras. Aside from the discussion here about how best to use my specific OSC cooled CCD, it's clear that they do offer advantages - the noise in a single sub is visibly lower, and with set point cooling you can easily use darks, which isn't realistic with a DSLR. Whether this translates to significantly better final images and whether that justifies the cost remains to be seen!

I'm realizing that I have a lot to learn - is there a good intermediate level guide that explains this? In particular, the relationship between the sky background level and read noise isn't something I'd considered. I assumed it was all about the signal from the target vs the background noise. Although I've never really looked that closely, I had a look at an un-stretched calibrated image from M33 from the ATIK 383L compared to a 550D. Same exposure time but different nights so entirely unscientific, but the ATIK is roughly averaging a value of 800 (in FITS liberator) in the center of the galaxy and maybe 600 in the dark background of the image. Readings from a similar image with a 550D are 2100 background and maybe 2500 in the center of the galaxy, which (albeit a meaningless comparison) would suggest a better SNR for the ATIK? However, I honestly never realized the image was so faint in both cases, so I'm starting to realize why this all matters so much!

Interesting, thanks. I'd basically settled on 5 minute exposures but not for any apparent reason other than it seemed like a lot compared to what my old mount count manage! I have an EQ6 that tracks relatively well, so it sounds like I should have a go at much longer exposures.

Last day at my old job today so found a little time for googling. Turns out the CCD on the 383L colour is pretty awful, with peak QE of 40%. I don't know how the QE is calculated for color CCDs (e.g. before or after the Bayer matrix is added) but this is on par with my DSLR so I guess the only real advantage of the 383L over a DSLR is that it's cooled and so much less noisy. Most other cooled OSC cameras list QE of 60% or more, so my naive understanding is that exposure duration would need to be 50% higher to capture as much light? Probably explains the bad reviews! That said, I much prefer to see how well things actually work rather than the numbers. If only it wasn't cloudy every night!

I doubt it's the best camera in the world (in fact, one forum post described it as the worst!), but it has a larger sensor that most of the other camera's I've seen for sale in this price range, and there are plenty of images out using it that are better than I was managing with my DSLR. I never understood exactly how the OSC color version could be that much worse than the mono version given it presumably has a similar bayer matrix to all other OSC, and like most of these debates, it's very hard to find actual evidence based comparisons. So far I haven't had much clear sky. It's noticeably (by eye) less noisy than the DSLR and the set point cooling means I can use darks. There's none of the fixed pattern noise I see on both my DSLRs. However, an hour of data on M33 did not produce better results than 3 hours with my DSLR (although I imagine the DSLR was in much better seeing and this weeks 383 data probably had fine cloud), so it's clearly not a step change in the way that I've heard people talk about their new CMOS cameras. My plan was to use if for a few months. I'm slowly working myself up to mono but I'd also like to see how much time I have once real life returns to normal. The good thing about buying second hand is that you can sell the item back and so you get to try stuff out pretty cheaply. In my search I also noticed that people are often extremely optimistic about the price of second hand cameras. 70% of new might be a good guide price for most equipment, but lot's of people expect to recover 80% of the new price of a 10 year old camera.

I got an Atik 383L+ for a little more than that. I considered the SXVR M25c too, but the two I saw on sale were a little more again.

Not sure I follow. I think the main plan is to hunt for extrasolar planets wherever they can find them. It's going to be easier to spot them near us. I also don't think you can extrapolate how long it takes life to evolve from a single sample (us).

Thanks both. I'll have a go at baking the tablet this weekend.

Thanks - I believe it's the oven rechargeable type. I forgot to also ask, I'm curious if anyone knows by what process this disappears after a short time - my guess is the desiccant traps water vapor, but once there is ice and the CCD is at -20, how does it dissappear?

Picked up a second hand ATIK 383L+ which seems to be working well. However, on both the last couple of nights there's been a transient blob on the first few images, which has then disappeared. One is attached below. The night before, there was two similar spots on the opposite edge. In both cases they were gone 10-15 minutes later. I'm guessing this is the sensor icing up? I'm going from ambient (10°C) to -20°C and then start imaging immediately. So was wondering: - does this look like ice? - is this normal, and can it be avoided by cooling in stages or just cooling then waiting 20 minutes? - does it suggest I need to re-charge the desiccant?

Success and a massive explosion. What more could one ask for!

Sorry, I thought you meant crop the images with a different number of pixels to align them!

Thanks all - stacking both in standard mode worked. Not quite the result I was hoping for, but I'll play around with various approaches tomorrow! I

Thanks - literally every time I reset the settings to the startools recommended, I change something when messing around. When you say crop the edges, how would I know how to do that? Don't I need exact pixel alignment? Apologies if that's a dumb question!

Thanks for the advice! I must be fundamentally misunderstanding. The first one I just went with intersection so I didn't have to crop borders. At least based on what DSS is saying, should the second step work? If not, what have I misunderstood?

Thanks. Dithering every 3rd frame or so seems like a decent solution.

Without suggesting it's a good idea, I'm trying to combine data from a OSC camera taken with two different filters - one is a dual band filter, the other a full(er) spectrum LP filter. To do so in startools requires them both to be aligned already and in theory, I can use DSS to do this. Camera resolution is 5184 x 3456. I dither so obviously the usable area is less. The process I have gone through is: - Stack the full spectrum data as normal in DSS in intersection mode. I get a file that is and leads to a perfectly decent result after processing. - Stack the dual band lights with the above file set as a reference frame, but unchecked in standard stacking mode. The offsets to the other files look good. However, the resultant file is full size. Is there something else I've missed?

I'm in Bingham so my scope is routinely pointed right above your house! Or at least it was, until the cloud settled in. Best of luck - if do you do discover any good dark spots that are good for observing nearby , let me know!

Apologies - I wrote this on my phone, accidentally pressed submit then the battery died. I've actually written the post now I'm home!

I've been using a DSLR so followed the advice to dither, but looking for advice with new cameras. I tend to take 300s subs and dithering adds about 30s to the time between subs (yes, this is a long time, but large DEC dithers upset guiding and it can take this long to settle). I've got a couple of new (to me) CCD cameras - one has setpoint cooling, the other doesn't, so just cools to around 30 degrees below ambient. The question is would you dither for either or both of these cameras? Both appear to have pretty low dark current compared to my DSLR. My initial guess is: - don't dither with the set point cooling, but create a dark library and use that - dither with the camera that lacks set point cooling, and don't take darks Anyone suggest something else? The random dark noise appears to be pretty low for both, but each had a small number of hot pixels on test darks. Obviously dithering can never be a bad idea, but it's costing me 10% of my exposure time.

I had the same idea. You can use https://astronomy.tools/calculators/field_of_view/ and with a rough estimate of the width of Saturn/Jupiter in arcseconds, work out how many pixels it'll cover. Even with a 2x barlow, with my DSLR you'd get 1.25"x1.25" per pixel, which doesn't lead to very large planets - I don't know how to work out how big the planets will be then, but Jupiter appears to get up ~45". I'll have to do some more research to work out how big a barlow you can use - the Dawes limit is around 1.6" and with a 3x barlow and my DSLR, you'd be at pixels of 0.83", so roughly a 2x multiplier. The internet seems to suggest up to 3x multiplier works, but seeing will almost certainly dominate, so I don't know if it'd make a practical difference. I'll need to check, but I imagine it'll be behind trees for me, so I'll probably pass. I had go at Mars with a DSO scope + barlow + DSLR in October but it didn't go well! I'm considering getting a different setup for the moon/planets in time for the summer, when DSO imaging will be harder due to reduced night.

The weather, the moon, and equipment that stops working on the only clear night of the month! Also weather apps - if you just go by what they say, you miss the nights that were forecast to be cloudy but turn out to be clear.

I enjoyed episode 1 but not 100% sure I buy the split between the Earth based evidence and the fictitious planet. I presume that the Earth based segments are easier to plan and cheaper to make than the alien planet segments! I've also read a lot of classic sci-fi and couldn't help but feel that episode 1 was a mish-mash of ideas I'd read about before. All in all, I'll keep going. For some reason I tend to prefer documentaries whilst I'm exercising indoors, so any new material is welcome - Netflix as a relatively small amount of high quality documentaries, and a long tail of rubbish!

I don't think it's necessary to expose for longer, although that's how many people in areas with heavy light pollution will use them. Even keeping exposure constant, you're getting a better signal to noise ratio.