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A Cluster of Globulars


PhotoGav

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I was zipping about the sky last night, despite the haze, wondering where I might point my telescope next. We seem to be in Globular Season! Here is a compilation of nine globs - compare and contrast! I still don't know which one I will go for and am slightly hesitant anyway as SGP struggles to autofocus on globular clusters, which means I have to offer some manual intervention to: slew away from the glob, run autofocus, slew back to the glob and resume the sequence... the horror of getting that involved in an imaging run!!

1322262136_GlobularMontage01.thumb.png.abec0926b893170f3f4fc18402cfb80a.png

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A really nice collection with surprising variation. Thanks for posting.

Does this count as 9 entries or one; for the 30 sec challenge? I like the overall effect of them all together. Almost like an old fashioned film contact sheet (don’t suppose many people remember those).

Paul 

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Thank you Paul. I tend to think with Globs that you’ve seen one you’ve seen ‘em all, but this proves otherwise! I do love a good glob through the eyepiece too!

Contact sheets - surely not old fashioned... it feels like only a few years ago that I was constantly poring over those, wondering which frame to put in the enlarger and print!!

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An excellent night's work Gav, glad to see that I'm not the only one hunting globs currently.

Like you I'm still having issues with SGP autofocus on globs, I wish they'd provide an alternative to the all FOV option, but despite the lengthy discussions it's clearly not a priority...!! It's particularly bad when shooting the very low down ones like M19 which I was trying a couple of nights ago, as the combination of poor seeing and poor autofocus is a nightmare. Here's a stack of 8x120 red taken through my C14 roughly processed and clearly not fully in focus....

M19_R_IP65.thumb.jpg.956935342f8286ce626f63e629e01e60.jpg

I trried refocussing, but then lost the target, so will have to try again another night. It was down at ~10 deg and only above my obs wall briefly, before diving behind a neighbour's trees, so a very tricky target for me to capture RGB. I think that I'll have to use an alternative target for focus, then turn AF off whilst it cycles through the filters, which are pretty parfocal anyway, to see if that's a better method for this one.

Yes, they are all a bit samey, but then maybe not, when you look more closely, as I posted previously with my collection from earlier this month. I particularly enjoy viewing them visually too....

Cheers, Geof

 

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@geoflewis - thank you! Don't get me started about autofocus and SGP... it is driving me a bit nutty. I'm not sure what the SGP developers are up to these days, they used to be extrememly responsive, but since the launch of version 3, they seem to have gone very quiet. I have a feeling that there are so many fundamental issues with their code that need to be addressed now the application has become so hefty, that all their work is focussed on recoding stuff rather than coding new features. I guess it has to be done to make the app more efficient and stable, but as a user, it looks like no progress is being made. Patience, patience... yet again! As for trying to image down at 10 degrees altitude - you've done amazingly well to get anything at all. I struggle to get much below the celestial equator and when I do dip down to the 20 degree region, it's a fuzzy spongey mess, even when in focus!!

@Mark at Beaufort - thank you Mark. I will endeavour to add M22 to the collection, though at a max altitude of about 15 degrees, it won't be up to much - see above!

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@PhotoGav - I'm sorry to have wound that SGP key in your back 😏. It is frustrating, but for the comparatively low price, SGP has transformed my imaging routine, so I just accept that AF for globs and some other targets is a bit challenging....!! FYI I've just processed (and posted) my M10 from the same session.

I used SGP AF on each filter and whilst I'm not sure if it completely nailed focus, it was good enough for me to update my Messier collection with an improved image.

Cheers, Geof

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Nice set Gav, are you aiming for a full set of Messier list images, I have a go now and then, just a record image but not bothered for a while.

It's nice to have a bit of hands on intervention now and then if only to stop you forgetting how.

I've been through a cycle of various autofocus software but recently been just using  Maxim, one star in subframe, large statistics, and the Lakeside utilities manual buttons, easy to get down to lowest FWHM and quite satisfying really if you like that sort of thing :grin:

Generally only do one filter a night so just check it a couple of times and have a mooch around with the bin's in between.

Dave

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Thanks Dave. Yes, one of my astronomy sub-plots is to image all 110 Messier objects, though it is not my main priority, just an eventual goal. The biggest problem is that quite a few of the summer targets are very low for me, right down in the dirty bit of the sky. I'll have to take my kit down to my place in Southern Italy one day to complete the collection.

I've been contemplating how to maximise the limited imaging time through the summer and globs seem to be a good option, despite SGP's best efforts to make it nigh on impossible. I don't mind a bit of manual intervention every now and again, but by about 2am I am generally rapidly nodding off!

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18 minutes ago, Davey-T said:

I've been through a cycle of various autofocus software but recently been just using  Maxim, one star in subframe

I've also considered using either Maxim, or ImagesPlus Camera Control focus routines for these globs as both allow me to select a star and use subframes and give good results.....

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I have to make do with the occasional trip to the Isle of Wight for a southerly view.

6 minutes ago, PhotoGav said:

but by about 2am I am generally rapidly nodding off!

One of the joys of being retired is staying up till dawn and then having a nap :grin:

Dave

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Just now, geoflewis said:

I've also considered using either Maxim, or ImagesPlus Camera Control focus routines for these globs as both allow me to select a star and use subframes and give good results.....

The Maxim autofocus works very well, I use it in preference to FM4 but normally don't bother unless setting up a sequence with different filters.

Dave

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4 hours ago, PhotoGav said:

Don't get me started about autofocus and SGP... it is driving me a bit nutty

 

3 hours ago, geoflewis said:

I used SGP AF on each filter and whilst I'm not sure if it completely nailed focus, it was good enough for me to update my Messier collection with an improved image.

Hi Lads, when I did M13 I was worried like you with the focusing powers of SGP, to alleviate the worries, firstly I double checked my focus points using RayD's video, even though I've done it loads of times, it nice to refresh my ageing memory: -

My Chroma filters are all parfocal except the green with is 20 units out, so I focus only with the Lum and tell it to refocus at every 3 degree variance, saves a hell of a lot of Agro and here was my result the other day of M13: -

Guiding was the only downfall but focusing was bang on.

Edited by Jkulin
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@Jkulin thanks for sharing the video tutorial by @RayD . I wish I seen that previously as my first few attempts at setting up SGP AF were mostly fumbling in the dark (literally as well as metaphorically). However, that's not my (nor I think @PhotoGav's) main problem, which is that SGP often (too often in my experience) interprets the cluster core stars as one or more large stars completely throwing off the HFR stats resulting in incorrect (sometimes wildly so) focus positions.

As others have mentioned Maxim (which I have used) and ImagesPlus which I also have, use single stars with subframes to calculate HFD, which always worked well for me, but I prefer the other sequence automation features of SGP to both of those other AP solutions. I now always monitor the SGP AF routine to be confident that it runs ok, before letting the sequence continue.

That's a very nice M13 BTW, which I'd previously seen, but looking at yours again got me reviewing my processing workflow to brighten the core stars, which looked rather dull and grey in my original version. FYI the revised version is up on Astrobin at https://www.astrobin.com/full/407729/B/

Cheers, Geof

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2 hours ago, PhotoGav said:

John - you managed to get good focus with SGP while M13 was slap bang in the middle of the field of view?

Hi Gav, I wouldn't say it was bang in the middle, as my intention was to offset, but as I was wary of SGP  and globular clusters I double checked my focusing with a Bartinov and all was good.

When I was subsequently chatting with my mate Peter, he uses Maxim and couldn't believe that SGP does not allow you to slew to an easier star/star system, focus and then slew back on commencement of the sequence, maybe I shoudl post that up on the Main Sequence forum?

Geof, not experienced any problems with Globular cluster focusing and have tried on a number but I have to admit when I saw the data coming down from M13 I knew it was really quite good, so double checked everything.

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1 minute ago, Jkulin said:

couldn't believe that SGP does not allow you to slew to an easier star/star system, focus and then slew back on commencement of the sequence

Thanks John,

SGP has a module called Focus Target, which allows you to set an alternative target for focussing which is different from the imaging target, so that you can slew back and forth between them as required for focussing and image capture, but it is a manual process that does not run in tandem with auto focus, so I have not used it - yet..!! It's on my list to try this summer, but really I want a fully automated solution that will cycle through filters without my manual intervention to refocus on filter change.

Cheers, Geof

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5 minutes ago, geoflewis said:

SGP has a module called Focus Target

Thanks Geof, I have never seen it before, so will try to find out more as that might well be the solution for globs.

Geof, what filters are you using as if like me they are parfocal then you only need focus with the Lum, I'll PM you

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6 minutes ago, Jkulin said:

what filters are you using as if like me they are parfocal then you only need focus with the Lum

Hi John, my filters are Astronomics, which are rated parfocal and appear to be so, but as I don't have anything to monitor temperatutre changes, I do generally opt to check focus on filter change and sometimes at timed intervals, e.g. every hour, just as a precaution. Ok to PM me and perhaps we could also have a brief telcon. Geof

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The Focus Target module in SGP is a manual thing and is useful, but ruins the automation that SGP is all about. I shot M2 last summer using the Focus Target module and sat there nursing the system through the whole process. It worked, but it was only semi-automatic at best!

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9 minutes ago, PhotoGav said:

Here’s the post with the M2 image from last year:

Hi Gav, thanks for posting that link and that's an excellent M2. I'm going to play with the Focus Target module in SGP, but one question I have is does SGP automatically run plate solve to ensure accurate centering of the imaged target after each Focus Target AF run? Did that make sense - basically how do you guarantee the accurate return to and centering of your image target after focus is done? Is that automated or another manual process? Cheers, Geof

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9 hours ago, geoflewis said:

Hi Gav, thanks for posting that link and that's an excellent M2. I'm going to play with the Focus Target module in SGP, but one question I have is does SGP automatically run plate solve to ensure accurate centering of the imaged target after each Focus Target AF run? Did that make sense - basically how do you guarantee the accurate return to and centering of your image target after focus is done? Is that automated or another manual process? Cheers, Geof

Re-centering on the imaging target having slewed to the focus target is indeed a manual operation. IIRC, I turned Autofocus off in the SGP sequence and set the focus reminder pop up. When it was time to focus, I paused PHD2, clicked the Focus Target button and the scope slewed to the Focus position (having set up the focus destination earlier - I can’t remember if the focus destination persists between session, I don’t think so?). I manually ran an autofocus routine. Once focussed I right clicked on the target name and chose ‘centre on target’, it did its thing and once back on target, I restarted PHD2 and clicked to carry on the sequence. A bit tedious to say the least, but at least you get sharp globulars!

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