swag72 Posted October 26, 2011 Share Posted October 26, 2011 This is my first light with my Atik 314L. I know that I have an issue with my focuser collimation, this is in hand and will be sorted next month - Apologies for the stars not always being round!I would welcome peoples comments and thoughts on this, as it is all new to me.Details - HEQ5, SW120ED with 0.85x reducer, Atik 314L taken at -5 degrees, Trutek supaslim filter wheel with Baader 7nm Ha filter.23 x 600s exposures - No darks or flats at this stage. Link to comment Share on other sites More sharing options...
ncjunk Posted October 26, 2011 Share Posted October 26, 2011 I think you´ve covered most of it...the stars aren´t quite round and because its slightly out the image isn´t as sharp as it could be.Apart from that (and the framing is a bit out!) what I want to know is where you got clear sky from its blowing a gale and bucketing down here in Galicia!Good first light though, very nice.ah just had a look on the map and you´re at the sunnier end of Spain! Link to comment Share on other sites More sharing options...
swag72 Posted October 26, 2011 Author Share Posted October 26, 2011 Cheers Neil - It was lovely and clear down here last night!!When you say that the image isn't as sharp as it could be - When I focused on Polaris prior to slewing to the target, I had an FHWM of 1.5 - 1.6. I understand that to be pretty good. So is the lack of sharpness being caused by my out of line focuser do you think?I'm quite excited at how large stuff is in the frame - I'm looking forward to bagging some smaller stuff when I'm all sorted. Link to comment Share on other sites More sharing options...
steppenwolf Posted October 26, 2011 Share Posted October 26, 2011 This is a very good first light image and you have already determined the 'problems' with it. The focus does look a little soft to me even allowing for the possibility of the focus assembly being out of true. I would also recommend focusing on a brighter star closer to the main event - in this case Sadr or Deneb would have been a good choice and at the risk of being shot down have you considered a Bahtinov mask for focusing? I find chasing FWHM a bit of a fools errand - but that's just me!Don't be fooled by the size of the object in the field of view, remember that you are using a much smaller sensor now - imagine cropping the same object taken with your DSLR to see what I mean.I think this is a great start and I'll bet you can already see the potential of Ha filtering on the right objects. Link to comment Share on other sites More sharing options...
ashworthacca Posted October 26, 2011 Share Posted October 26, 2011 Sara, although it does look a little out of focus the detail you have captured is superb. The low amount of noise in the background is also impressive. Looking forward to see how you get on with this CCD as I thinks it's my next purchase.---I am here: http://maps.google.com/maps?ll=53.544866,-1.487083 Link to comment Share on other sites More sharing options...
ncjunk Posted October 26, 2011 Share Posted October 26, 2011 When you say that the image isn't as sharp as it could be - When I focused on Polaris prior to slewing to the target, I had an FHWM of 1.5 - 1.6. I understand that to be pretty good. I was just thinking that if your star shapes are out then the main target will also suffer some blurring (for want of a better expression).I use focus max now so it determines the best FHWM for me based on a stored sample (you have to let it calibrate and it takes FHWM values either side of focus creating a curve which represents the FHWM versus focuser position...12 of these curves as a minimum)The FHWM can be a bit misleading as depending on the star it may be a larger number (on my C11 at F6.3 I was getting a FHWM of 3.9). What I used to do when doing it manually was get the FHWM as small as possible and then double check with a Focus Mask.I would sort out those star shapes first and then have a play with the focus (the focus you have is good enough) Link to comment Share on other sites More sharing options...
johnrt Posted October 26, 2011 Share Posted October 26, 2011 Looks very good to me, especially or a first night out with a new camera.Any particular reason you are only chilling to -5? Link to comment Share on other sites More sharing options...
swag72 Posted October 26, 2011 Author Share Posted October 26, 2011 I do use a Bahtinov mask Steve - I focused using that and it gave me a FHWM of 1.5 - 1.6. I am struggling to know what stars to focus on as it appears to make a massive difference depending on which you pick. For example, the first time I tried to focus I used Vega and that just produced me a big bloated circle that it was really hard to focus on with the mask.The reason I used -0.5 was because my ambient temperature last night was showing at 19.6 degrees. I assumed that as the 314L goes down to 25 below ambient I was on my limit. I will try next time just to get it to it's lowest. Link to comment Share on other sites More sharing options...
steppenwolf Posted October 26, 2011 Share Posted October 26, 2011 the first time I tried to focus I used Vega and that just produced me a big bloated circle that it was really hard to focus on with the mask.Funnily enough, I've been using Vega (and Deneb/Sadr and Altair) all summer but the key to this is to reduce the exposure time accordingly. Try again on Vega with the Ha filter in place but use an exposure of 4 seconds, binned 2 x 2 - this should suit your current setup very well and you should get a really good set of diffractions from the Bahtinov mask. Link to comment Share on other sites More sharing options...
prokyon Posted October 26, 2011 Share Posted October 26, 2011 Hi Sara,nice 1st light with the new cam. I don't know if you hit the focus or not. I think you have a little dumping. The stars in the coner at lower left are a little elongated but in the corner top right they are okay. Link to comment Share on other sites More sharing options...
swag72 Posted October 26, 2011 Author Share Posted October 26, 2011 Funnily enough, I've been using Vega (and Deneb/Sadr and Altair) all summer but the key to this is to reduce the exposure time accordingly. Try again on Vega with the Ha filter in place but use an exposure of 4 seconds, binned 2 x 2 - this should suit your current setup very well and you should get a really good set of diffractions from the Bahtinov mask.Will give that a go Steve - Cheers. @prokyron - 'dumping'? I have a focuser that I don't think is square in the OTA - Many people spent many hours on here helping me diagnose what I hope is the problem! I just wanted to get out and play, despite the issues I have! Link to comment Share on other sites More sharing options...
ncjunk Posted October 26, 2011 Share Posted October 26, 2011 Just have a play and get some different targets, if you´re not carefull you´ll spend too much time worrying about all the little problems and not enough time having fun! Link to comment Share on other sites More sharing options...
steppenwolf Posted October 26, 2011 Share Posted October 26, 2011 I'm with Neil on this - just get on and experiment, sort out any issues when the conditions are poor (do you have poor conditions down where you are?). AP is fraught with problems, it's all part of the fun but make sure you don't miss out on the real fun bits like capturing a first light that most of us would have been thrilled to have got first time out. Link to comment Share on other sites More sharing options...
ollypenrice Posted October 26, 2011 Share Posted October 26, 2011 I use a Bahtinov as well, Steve and Sara, but in my seeing it is pretty useful to do a final tweak in FWHM I think. I do this though I don't know if it really helps, but I'm nerdishly addicted to the process now and couldn't sleep if I hadn't done it!I use 3 to 4 sec unbinned subs for FWHM and can usually get from, say, 1.2 from the mask down to maybe 1.1-ish with FWHM. Obviously it varies from night to night.Another FWHM bonus is that you can do it on any pettyfogging little star in the picture. No need to focus check by moving away. In fact Artemis leaves your FWHM selection in place from the first time so you can go straight back to that.I'm a fan.Anyway it's a great first light. OK, you need to sort the focuser but we know about that!! I too think focus is soft. But all things considered you'll soon be flying.I trust you're smiling?OllyPS, Steve, c'mon, we just love fiddling with our Feathertouches, now don't we??? Link to comment Share on other sites More sharing options...
swag72 Posted October 26, 2011 Author Share Posted October 26, 2011 Thanks guys!! Now leave those Feathertouches alone!!It is tricky though learning new things, programmes and camera's, so I'm not too unhappy with this and look forward to better things to come. You know Steve we do sometimes have bad nights!! Link to comment Share on other sites More sharing options...
steppenwolf Posted October 26, 2011 Share Posted October 26, 2011 PS, Steve, c'mon, we just love fiddling with our Feathertouches, now don't we??? Link to comment Share on other sites More sharing options...
johnrt Posted October 26, 2011 Share Posted October 26, 2011 There is no replacement for some time outside with a camera - I found the swap from DSLR to CCD a surprising jump.I wish my first image with my 314l looked like this one. Great things to come I think. Link to comment Share on other sites More sharing options...
Uranium235 Posted October 26, 2011 Share Posted October 26, 2011 Sara, its perfectly possible to focus on any bright star if you change the settings in Artemis caputure. 1) Select any bright star and slew to it, leaving your camera on a 3x3 bin in Artemis caputure, 0.5s loop (dont check autosave...lol).2) In artemis capture, use the subframe definition tool to draw a decent sized box around the star3) Pop on the Bahtinov mask4) Stop the loop, change the binning to 1x1, restart the loop (still at 0.5s), zoom into the star5) Uncheck "Autostretch"6) Move the whitepoint slider to the right, until you achieve the below pattern (minus the dotted lines and arrows of course) You will know your focus is good if you have clear space between the three dots either side of the central dot. It can be tricky to achieve, just be patient and never think "close enough" is good enough. The arrows indicade the direction of travel when you adjust the focus.Forgive the crude diagram, but I hope you get the idea Link to comment Share on other sites More sharing options...
swag72 Posted October 26, 2011 Author Share Posted October 26, 2011 Thanks for that - Obviously I have a few things to work on for focus!!! Link to comment Share on other sites More sharing options...
AndyUK Posted October 27, 2011 Share Posted October 27, 2011 Re: focusing, can I ask if anyone's managed to use Bahtinov Grabber for NB focusing?I've found L (and RGB) filter focusing with a B mask on a bright star pretty simple - A nice "whisker" picture to play with and "Bahtinov Grabber" seems to work pretty well, but when swapping to a NB filter, using the B mask is MUCH trickier and as opposed to getting a nice 6 pointed star image, I end up with a "dot-to-dot" version(?) in Artemis, and presumably as the star image is more grainy, "Bahtinov Grabber" then struggles. It is still possible to focus just using the Artemis screen, but I have to squint at the screen a little (even when zoomed in) and I never feel quite 100% that I've got the central row of dots splitting the angle of the outer row of dots.Admittedly, I've only been using 2s unbinned to date, so it may well be that I just need a longer exposure (and binning), but I just thought I'd ask to see if anyone's using "Bahtinov Grabber"with a CCD? Link to comment Share on other sites More sharing options...
Uranium235 Posted October 27, 2011 Share Posted October 27, 2011 Ive not tried the B grabber yet, ive always gone with a short loop with a 1x1bin subframe (quicker readout time) - and done the "dot to dot" version. As long as there is equal clear space like in the diagram, it works every time. It even shows how far your focuser shifts when you lock it as the feedback is in real time. Link to comment Share on other sites More sharing options...
RobH Posted October 27, 2011 Share Posted October 27, 2011 Very good first light Sara...there's lots of depth in there.Re. focusing....I used to use Focusmax and robofocus, but, TBH, now I just slap a Bahtinov mask on and focus by eye....seems to work OK.What's Bahtinov Grabber?CheersRob Link to comment Share on other sites More sharing options...
AndyUK Posted October 27, 2011 Share Posted October 27, 2011 Hi Rob - Bahtinov grabber for any camera Niels Noordhoek’s weblogIt basically takes the guesswork out of assessing exactly when the central line bisects the angle of the other two. When you fire it up, a window appears on screen. You then select the option to "grab" the bahtinov mask pattern from the capture software (ie Artemis). You drag a box around the B mask pattern which then appears in the Bahtinov grabber window... with a load of coloured lines that (apparently) show you which way you need to focus. As you change the focus, the image not only changes on the capture screen but also the "grabber" window, and when it's totally IN focus, the B mask pattern is suddenly surrounded by concentric circles.I used it once with an L filter in Artemis and it worked a treat, but I haven't got it to work yet with Ha... Link to comment Share on other sites More sharing options...
RobH Posted October 27, 2011 Share Posted October 27, 2011 Thanks Andy....I'll have a look at that.CheersRob Link to comment Share on other sites More sharing options...
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