The Lazy Astronomer

2 laptops, a large toolbox and remote desktop connection over wifi - scope side laptop sits in the closed toolbox and I go indoors. The only 'dew' I worry about then is the condensation on my beer 😁

Glad you got it sorted, now let's see the result!! 😁

Don't take that calculator as gospel, with typical UK seeing conditions and a decent-ish mount, you'll likey be correctly sampling with any of the cameras mentioned at focal length of around 350 - 400mm.

Based on my own experience, the answer to your question is very simple: how many attempts does it take? n+1 😜

I'll add my personal experience, which will pretty much agree with vlaiv's advice: I use an Esprit100 (550mm FL) with a 294MM (4.63um pixels), which gives me an image scale of ~1.7"/px. My guiding is usually 0.5 - 0.7", and my measured FWHM usually leads me to bin my stacked image 2x2, so I'm already oversampling and l can't see any particular advantage to me to increase my focal length with my typical seeing conditions (making the assumption the sky is my biggest limiting factor in ability to resolve detail). In short, based on my experience, I think you'll be quite happy with the above recommended image scale from vlaiv, and the FOV afforded by an APS-C sensor with 400 - 500mm of FL should be quite adequate for the majority of nebulae and the larger galaxies. Just be aware though that galaxies (excluding M31) will appear somewhat small in the full frame of the image, but you can always crop the image.

I don't think it's actually stacked anything. When I last used DSS (which was a while ago, admittedly), the blue-white bar along the top would display some text saying something like "n of n frames stacked". I don't see that in your pictures.

Same here, if you're looking for a OSC APS-C, I'd suggest the 2600 over the 071

I would hazard a guess that you'd want the higher frame rate, although happy to be corrected if there are other factors at play to consider.

To actually answer your question, 1.25" is fine for a 4/3 sensor for at least f5.5**, provided you can get the filters close to the sensor - i.e. zwo camera with a zwo filter wheel. **my setup is a 294MM (4/3 sensor), with a zwo 7 position FW (Astronomik 1.25" mounted filters ), connected as described by zwo, and it works, but flats*** are needed for vignetting. ***don't even get me started on the topic of getting good flats for the 294!!!

I've made references to this show before* and no one's really got it, but I'll try again... Go mono. *this time it's a reference to a reference, so extra obscure. The fact that the gif has no subtitles to accompany basically limits it to mega fans as well, so even more obscure.

I wondered how long it would be before 6 spiked stars were the new 'in' thing!

I've just looked that up (before my time), and on the scale fairness, yes, that's several orders of magnitude more unfair!! 😁

Doctored is unfair term to use; it implies what is being presented is not real. Without doubt, there are some unscrupulous imagers who use something like Photoshop to add in detail that isn't there (or remove detail that is there), and/or attempt to blend in Hubble data and pass it off as 'their image' with a view to trying to impressing others, however the vast majority of imagers will not do that, because, well, what would be the point? Post processing is an absolutely vital part of astrophotography because the amount of light captured is very, very low compared to daytime photography - an example below is of a hydrogen alpha image of M16 I captured last year: This is the data basically as it comes out of the camera (well, not quite, it is calibrated and stacked, but it has undergone no post processing). Not much to see really, just a few stars and a hint of the pillars. This next image is exactly the same except it has undergone some stretching to better visualise the data: Nothing added, nothing taken away, just essentially brightened in a non-linear fashion to allow us to see the information that was captured.

It's a toughy - each one seems to show off something different! I think I'd go last one as well.

Yep, starry version for me too, looks almost a bit cartoon-like without them

Not your camera, but the principle should be the same for the cabling:

Hmm, very interesting! I may have a bash at this myself at the weekend. Processing IR data seems appropriate during the hottest weekend of the year. Out of curiosity, what was the raw data like to work with?

My instinctive reaction is it probably wouldn't be worth the time required just for a pretty picture (if it would even turn out that pretty anyway). We would probably need somebody with a larger aperture, dual rig setup, who has a penchant for undertaking different and interesting imaging challenges. Now, if only there was someone like that around here... 🤔

Is it weird the thing I want to know most is their noise reduction routine? 😅

It's not overexposed in the sense that it doesn't appear to be clipped, but nevertheless, I'd start by saying that unless you have a very dark sky, 600 is probably overkill - you could likely drop down by half or more. As an example, I typically use 30 - 60s for broadband and 3 - 5 mins for 6nm narrowband (I have a pretty typical suburban sky). Second, no need for bias and darks, the bias signal is already contained within the darks. I've also seen people with this camera do it the other way around and ditch the darks and just use bias instead as there's no amp glow to worry about. I can't comment much further on that as I don't own the camera myself. If pushed I would probably have a preference for using darks only instead of bias only, but then I may be, uh, biased (no pun intended) by my current camera experience (294MM, so I've got serious amp glow!!) I whacked it through a quick bit of stretching using the GHS script in PI, followed by a saturation boost - I've probably not done it particularly well, as I'm not currently on my processing PC, but on a laptop which I know for a fact has a poor display. Hopefully it's an indication at least. How does it compare to what you were getting?

Unfortunately, with your current lens, M51 will never be anything more than a tiny fuzzy grey speck, regardless of integration time. Most galaxies have a very small angular diameter, so will appear very small in images. A telescope with a focal length of 500mm+ would probably be the minimum needed to get decent detail on some of the larger ones*. However, be aware that the longer the focal length, the more difficult (read: expensive!) things get. *A notable exception here is Andromeda, which is one of largest things in the sky - this would actually be doable with your existing setup. It would still be quite small in the image though, as shown from the FOV calculator image below (https://astronomy.tools/calculators/field_of_view/), but wide shots like this can help to give context to a deep sky object. I did a quick Google image search for Andromeda through a 50mm lens and found this image, so this is as idea of what you can expect: The owner of that image stated an integration time of <10 minutes, so I'd imagine more detail could be brought forward with more imaging time.

It was taken through an Evoguide 50, which is a doublet. I also used an Astronomik L3 filter to cut the extreme ends of blue and red to reduce CA a bit.

50mm lens unsuitable sure, but galaxies need not be only the reserve of long focal lengths - the below was taken at just 250mm. Not an award winner by any stretch of the imagination, but larger scale structure clearly visible on what is a very small target.

It's definitely there, but very very faint. I think I would have expected more from 17hrs - I'm left wondering if your filter bandpasses are not as advertised at f4 (know anyone with a spectrometer?)

I agree, very dramatic! I normally prefer the hubble pallette for this object, but you've got great depth in the reds here - I like it.