Phillyo

IDAS NBX, it's made for fast focal ratio imaging down to F2. I have one for my Samyang 135, though I haven't used it much yet. I did a test with a single 2 min exposure and the Ha was very evident. Waiting for clear skies to try more.

How would I connect them together though? I did see that on FLO but couldn't figure out how I would connect the 577 dovetail onto that one.

So this is a long shot, but I've been mounting my Samyang 135 via the Astrokraken set up (http://www.astrokraken.fr/bracket-system-for-samyang-rokinon-135-f-2-telephoto-lens-a183920490) and using an existing Manfrotto 577 connection on my Astrotrac. Well, I'm hopefully buying a HEQ5 Pro to mount it on and I'm wondering if anyone knows of a way to mount the Manfrotto 577 mount onto the vixen plate on the HEQ5? Am I going to need to order then Vixen dovetail from Philippe (Astrokraken) for it to work or is there an adapter I can use to attach the 577 to the vixen? Yours in hope. Phil.

Thank you both. Looking forward to adding a lot more data to this to try and find the faint stuff! Phil

Having stopped about 5 years ago, I decided I missed astrophotography (remind me why!?). Many teething issues with kit not talking (ASIair Pro) and whatnot but I finally managed to get out last night and get about 300 x 60s exposures on M45. As I'm using an Astrotrac at the moment I'm limited to about 2hours or shooting before it has to rewind. Trying to reframe the shot again to get it close to the first 2 hours is pretty much impossible, so I had to crop it a bit to get rid of the edges. Anyway, kit was ASI533 with Samyang 135/2 @f2.8. Mounted on the Astrotrac and captured with the ASIair Pro. Processed in Pixinsight (that was a cold sharp remind of what I'd forgotten too). It's not incredible, but I'm happy with it as a first image back. Lots of room to improve though! Next upgrade will be a goto mount lol. AZ-GTi maybe? Thanks, Phil.

I would say yes, but also I would say no? Unless your DSLR is cooled then making a dark library may only make things worse. Darks need to be captured at exactly the same temperature (and exposure time) as the light frames. Cooled astro cameras can do this but DSLRs can't. I personally wouldn't bother adding darks to the calibration for a DSLR. Just use Flats and BIAS frames. Phil

I would be more inclined to accept the eggy stars at the edge of the field if I was using a full frame sensor, but a 1" sensor that 'crops' in so much, I would've expected a flatter field. I will mess with the spacings as I think I have some delrin spacers somewhere and see if it improves things next time I have a clear sky. Maybe sometime in 2021. Thanks all for the input.

Good afternoon all, So I managed to get out very quickly last night under not ideal circumstances but I wanted to try out my new set up and get the teething issues out of the way. I'm wondering if anyone could tell me if this is sensor tilt or spacing issues maybe? All the stars point towards the centre of the frame, but CCD Inspector doesn't show what I expected to see? There was some very thin high cloud so it wasn't perfect but wanted to give it a shot. ASI533 with Samyang 135/2 @f2.8 connected with the ZWO Filter Drawer for Canon EOS lenses. Thank you, Phil.

So I went out last night and set everything up (with some hiccups but that's an issue for another day). I polar aligned nicely with sharpcap then moved the lens towards the east where I'm going to be imaging M45. I ran the Histogram/brain function in sharpcap and it did some tests and told me that for my set up my optimal exposure time is 3.2 seconds. What? System setup = ASI533, Gain 100. Samyang 135/2 @F2. No filter other than UV/IR. Surely 3 seconds isn't going to really catch anything useable is it? I ended up setting it to 2.8 for rounder stars and leaving it doing 1min exposures but the clouds came over and I packed up and went to bed. I'll have a quick check of what I got last night (not much) but apparently 60 seconds is WAY too much. I've made a post on the sharpcap forums too so hopefully Robin will be able to confirm that 3.2s exposure time but it seems very fast! I know the 533 is sensitive and at F2 I'm catching lots of photons but still!! Interestingly the exposure calc in NINA gave pretty much the same result. Phil

Thanks Tomato, I've been drooling over @gorann's photo's the last few days so I'll definitely keep an eye out! Look forward to seeing your experience with this filter Gorann!

Having done some research online (should maybe have done this sooner, sorry!) it seems the IDAS NBX was actually made specifically for faster focal ratio systems, so I've ordered one of those instead. They're on back order too at the moment I believe but hopefully once it's in stock I can give it a shot and see how it performs! Phil

Good evening, So I had an Optolong l-extreme filter on order to use with my ASI533 and Samyang 135/2 system, however I have just watched a video on youtube where a guy was using that filter with a RASA at f2 and was getting next to nothing in the Ha channel until he dropped it to f6.3. He linked this document: http://karmalimbo.com/aro/reports/Test Report - Optolong L-eXtreme Filter_Aug2020.pdf which shows that at f2, it has as low as 10% transmission at f2 so I have cancelled the order for now (it's on backorder anyway). I'm wondering if the IDAS NBX filter would be a better option for faster systems? Does anyone have any experience with either filter at fast focal ratios or know of any information I could read about them? Thanks in advance. Phil.

Any particular reason you're going with the L-enhance over the L-extreme, especially for Bortle 8 skies? No judgement, just curious.

Hi, thanks for the reply. I don't have the lens yet so I can't do any actual imaging (plus it's cloudy) so I was just trying to do the maths to get a rough idea first. Thanks. Thanks Alan. I gues I wait until all my kit is here then try doing some actual measurements, see what it comes back with.

Good evening all, Just reviving this post as I'm very confused (nothing new there). I've just taken receipt of my lovely shiney new ASI533 and I plugged it into sharpcap to run the sensor analysis thing and to try and calculate my sub exposure lengths. My back garden has an SQM of approx 20.50 (according to the lightpollutionmap.info website). I've used Dr Robin Glovers calculations here http://tools.sharpcap.co.uk/ with an F ratio of 2 (Samyang 135/2 lens), pixel size of 3.76 and a QE of 80% to give a result of approx 6 e/pixels/s. Once I put that calculation into his 10x(R^2/P) where R = Read Noise (electrons) and P = Light pollution rate (e/pixel/s) I get a calculation of 10x(1.5^2/6) = 3.75...I'm assuming that's 3.75 seconds. Now according to his presentation, for an RGB sensor you would then multiply that by 3 to give a grand total of 11.25. So that means I need to take photo's for approx 12 seconds. That can't be right surely!? That's at gain 100, which I think is unity gain? I know I can pay to get the pro version which will do the calculation for me when I point it up at the sky but a) it's cloudy (again) and b) my Samyang lens hasn't arrived yet so I can't do that. Help? Please?

Beautiful work, very nicely processed too. Subtle yet striking. Love it. Definitely prefer the left version.

I'm trying to find out if the ZWO ASI533 with it's 6.5mm back focus is able to connect to Sony FE lenses (135GM, 70-200GM, 55 1.8 etc) and if so how? I can't seem to find anything out about it. ZWO used to make an adapter for the ASI1600, 294, 183 and 174 but it has been discontinued. Any help would be greatly appreciated. On a side note, if the answer is yes I'll kick myself as I've just sold my Samyang 135FE mount because I thought it was a no go! Phil

That's true. I always used OAG so my guiding was done at the same focal length as the imaging.

If you're using a DSLR, unless it's cooled, I wouldn't bother with dark frames either. Temperature variances can often mean that using darks as part of the calibration and integration frames can cause more problems than not.

Nice image. No feedback regarding that because I don't use photoshop to edit. Maybe more data (you don't say how much you have?) will help clean things up a bit. Regarding the guiding, my understanding is that the amount of error that is permissible is based on the resolution of your system. For example if you're using something like an ASI533 with a 135mm lens then your resolution is going to be somewhere around 5.7"/pixel. So as long as your guiding is less than that, your stars will be round. If, however you're using the 533 with a Celestron 8SE with a focal length of over 2meters, then your resolution is going to be closer to 0.4"/pixel and your guiding needs to be bang on or you'll see eggy stars. To be honest, at that resolution you're likely to be more limited by the sky conditions like seeing and clarity than anything else. That's my understanding anyway! Someone may come along and correct me Phil

Good afternoon, Silly question here, having never used a cooled CCD camera other than a QSI 583wsg which has the built in filter wheel, I'm a little unsure how to connect my setup together when it arrives. I have the ASI533 coming with a 2" UV/IR filter and a 2" Optolong L-eXtreme filter which will be connected to a Samyang 135. I have read the manual and it says that the camera just requires an EOS-T2 adapter (which I have a couple of) and that adding the 2" filter between adapter and canon lens is 'optional'. Will the filter just screw in to the EOS-T2 adapter? Do I need anything else to make it work as I'm not sure how it'll screw in or slot in etc. Would I need to buy something like that ZWO EOS-T2 with integrated filter slot? The reason I went with the 2" filters rather than the 1.25" was future proofing myself and I'm also probably going to buy the Redcat 51 in the coming months (whenever they're back in stock!) and that has an integrated filter slot. Thanks for the help. Phil.

This might be a daft question, but would it matter if the test image(s) to find the best ADU value to imaging time ratio were taken with a none tracked mount? IE, would star trailing cause the image to be brighter than it ordinarily would be if the image was tracked? Thanks, Phil.

I have nothing of value to really add to this but I just wanted to say that this thread has been a super interesting read (along with the linked thread for the calculations). I'm getting the 533 soon so it's also very applicable to my situation! Thanks Alan for taking the time and effort to explain all of this to us mere mathematician mortals! Phil

Ahhh perfect, thank you Alan! I'll go take a look.

Hi jambouk, Thanks for your reply. If I use this style of connection will I still be able to use my 2" uv/ir filter?