The Lazy Astronomer

I think this is going to come down purely to cost. You will get more sensor for your money with a DSLR for sure, but if you're buying specifically for astro, a cooled astro cam may well be the better investment. If you could find a good second-hand modded DSLR, you probably wouldn't lose any money on resale if you did decide to upgrade again in the near(ish) future.

Interesting! Any news on a potential release date yet? I had heard Ivo was also working on an amazing new deconvolution tool for the next major update too, so looking forward to that

Thanks very much. Judging by the responses here this is certainly my most popular image to date, so I've clearly done something right! I really like the other images I've seen of this target with the huge expansive OIII shell around it, so definitely something I'll be revisiting once I manage to pick up an OIII filter.

Thank you! I was reading the unofficial Startools manual which has suggestions for different ways to add Ha to RGB data, and did indeed settle on using layers as the best way. I use the asi294mm camera, which produces some very interesting patterns on Ha images, so I wanted to make sure they weren't interfering with the image. That said, it probably would have been fine without any flats - to be honest I think it became more about making sure I could get it to properly calibrate, rather than needing to.

As has been mentioned, a focal reducer will not affect the amount of light your setup will gather, what it does do though is twofold: 1. It spreads the light over fewer pixels. This means that for a given scope and camera combination, it increases your signal to noise ratio. Theoretically, this allows you to create an image of a given 'quality' (for lack of a better word) in less time, at the cost of some resolution. 2. It widens your FOV, which can be useful if you are unable to fit a particular target nicely in the frame. The same effect could also by achieved shooting a mosaic (without a reducer) and binning the data in post processing.

Thanks ☺ All post processing was done in Startools

Spent a few nights collecting some data on M27 to see if it was possible to get the faint halo (perhaps stupidly, on some of the shortest nights of the year). It was barely visible in the broadband data, but came out quite clearly in Ha, so that's where I focused a lot of my efforts. Had a nightmare with the Ha flats which weren't properly correcting the lights. It was especially weird because these were the same flats I had used twice previously with no problems, but anyway, after some reading I reshot the flats and corresponding flat darks with the cooler on and set to same temp. as the lights (previous ones were at room temp. with cooler off) and, hey presto - successful calibration! Still no idea why the room temp. flats worked fine on the other two images though, so if anyone has any theories, I'd like to hear them. On to processing, and it took me ages to find a way of blending the LRGB and Ha in a way which didn't mess up the colours too much - I've settled on this which I'm pretty happy with. As always, any comments or thoughts welcome. L: 48 x 2 min, R: 15 x 2 min, G: 13 x 2 min, B: 15 x 2 min, Ha: 36 x 5 min. 6 hours, 4 mins total integration time, split pretty much evenly between Ha and LRGB.

What's your imaging scale? And how do your images look? Nice round stars or noticeable trailing? What I'm getting at is if your images are good, don't worry too much about the graph.

The 294 mono sensor is known to create some 'interesting' narrowband flats, but lrgb should look normal. I'm having a similar issue at the minute with my asi294mm - I have some flats (which I have used successfully on 2 previous images) which are now not fully correcting the lights. Going to experiment a bit this afternoon to try and figure out why.

And this is precisely where the difference of opinion will be. One school of thought will champion high quality of data, the other, sheer quantity of data. I've seen real world tests which conclude quantity wins out, but equally I've seen other tests which conclude the opposite. l don't think it's necessarily a question with a simple answer.

@Freddie beat me to it! You'll likely get varying opinions on this, mine is as above - 'suck it and see' as my old boss used to say.

Apologies if I've misunderstood your question, but when people talk about modding DSLRs, they usually mean removing the internal filters to allow more of the red end of the light spectrum (especially the hydrogen alpha emission line (656nm)) through to the sensor. Depending on how restrictive the internal filter was, it can greatly increase the number of photons detected from emission type nebula. The only downside is it will mess up your white balance for any normal photography.

Hi vlaiv, sorry I'm being super lazy by asking you instead of looking it up myself, but what's the calculation you are using to get to these sampling rates?

Still new to all this business, so I'm out at every opportunity. A couple of images to show for it at the minute, both in Ha only: 1 hour and 10 minutes of M16, and 3 hours of the elephants trunk Currently working on M27, trying to see how much of the faint halo it's possible for me to get. Only problem is, there's so much interesting stuff coming up now that it's difficult not to get distracted away!

Yes, l didn't want to name them specifically as the last thread about them ended somewhat controversially. In any event, I have no first hand experience of them, so can't pass any comment.

If this is on your eq6r, you probably could go longer - I managed to squeeze 3 minutes at 250mm (unguided) out of mine, but had to throw away about 1/3 subs due trailing caused periodic error in the mount. I never tried running periodic error correction (PEC) training though, so that's something you could look into if you run into that problem. That said, whilst you could go longer, do you need to? Consider watching this video of a talk by Robin Glover (Sharpcap creator) concerning sub exposure lengths:

As others have said, it's normal, and mine's the same. Generally not too fussy with getting exact balance and guiding performance is pretty similar from night to night, so doesn't seem to matter too much. If you did want to improve it, you could strip and clean the bearings and then repack with a lighter grease. The other alternative would be to get the mount tuned by a company (very pricey though).

What type of light pollution have you got? If sodium/mercury street lights, then you'd probably see a benefit from using a light pollution filter, if you've got a lot of LED type lighting around, then I'm afraid there's not really much you can do to surpress it, unfortunately.

You will probably need a uv/ir cut filter, yes, although other users of that lens will be better placed to confirm. I'm not sure how well corrected the optics are, but if its less than perfect, you'll probably want to look for a filter which cuts above just 400nm and just before 700nm. The Astronomik L3 filter worked well for me when I was using an ED doublet: https://www.firstlightoptics.com/uv-ir-filters/astronomik-l-3-uvir-blocking-luminance-filter.html Here is a handy calculator to check what filter size you'll need: https://astronomy.tools/calculators/ccd_filter_size. I put your equipment info in, and you should be alright with 1.25" as long as you can get the filter no further than about 25 - 30mm from the sensor. And lastly, yes, you should add 1/3 of the filter thickness on to your backfocus requirement.

I've just checked mine after having read through this thread, and there is a small amount of lateral play, however it really doesn't seem to cause any issue during use. Phd2 reports typical RMS of 0.6 - 0.8", which I probably could improve if I spent some time tweaking settings, but don't really have a need to presently (stars look nice and round, plus my image scale is 1.74"/px). I would advise trying it out and seeing what results you get before worrying about it.

The London Astronomer has a good guide to planetary imaging to get you going. I followed that advice last summer and got some pretty decent results. https://www.thelondonastronomer.com/it-is-rocket-science/2018/6/7/a-quick-guide-to-planetary-imaging

That is quite incredible for just 45 minutes!

No Spaced fans in?

I will clarify my statements by saying I have only actually been guiding for the last month, so probably have no idea what I'm talking about! That said, I see no need to recalibrate unless the guiding isn't good. I calibrated once, ran the guiding assistant for 15 minutes or so and accepted all its recommendations. For every session after that, all I've done is select a star and started guiding. RMS is generally in the region of 0.6 - 0.8". Could it be better? Probably. Does it matter? At my image scale, not really.

😨 Maybe you should be considering a gun! Or perhaps something else that will make a similarly loud bang to scare them off? Mostly. If you're headed out with some particularly expensive equipment, you should beware Gramsci. Rumour has it he roams wild on Hampstead Heath... +1 for anyone who gets the reference.