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Virgo Supercluster - Part II (of many!)

Uranium235

By Uranium235
in Imaging - Deep Sky

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Uranium235

Uranium235

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Right, now to go with the subs I took at SGL XI, last night I re-assembled the gear to make the most of a decent sky.

However, its a shame the same cant be said of my local light pollution - which compared to what I got at Lucksall, almost made it not worth bothering with (the difference was like chalk and cheese!). But I pressed on regardless and managed to get up to six panes - albeit not in equal exposure lengths as a couple of them are about 40 or 50min short.

Its getting increasingly difficult to get a handle on the gradients im getting, and stitching them together is taking ages! But, I'll try and stick this one out and gather the remaining data when the next new Moon comes around. I thought I might be able to find a reference image I can register to, but to my surprise it seems that very few people have attempted to cover this area - so for now, this is what I have:

 

Thanks for looking! :)

 

25794373635_9c039bed76_k.jpg

 

Fullsize:

https://farm2.staticflickr.com/1635/25794373635_de3597e987_o.jpg

 

 

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Uranium235

Uranium235

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2 minutes ago, michael.h.f.wilkinson said:

That looks really great!

Thanks Michael :)

It looks alright on the "thumbnail" above, but the fullsize shows the noise a little bit on the panes that were short of data - it will come together.... eventually!

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pipnina

pipnina

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Just now, Uranium235 said:

Thanks Michael :)

It looks alright on the "thumbnail" above, but the fullsize shows the noise a little bit on the panes that were short of data - it will come together.... eventually!

It's coming together! Already a great image!

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pipnina

pipnina

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Just now, Uranium235 said:

Haha... thats a good joke! :D

Im just going to hammer it in Lum for now to get it clean ;)

 

You'll only get the Lum finished if the weather gods don't notice you outside with a telescope!

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Uranium235

Uranium235

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Just now, PhotoGav said:

What are the scope and sub length details?

Its from the Star71, and 10x600 per pane but a couple only have an hours worth of subs... and its of mixed quality, I'd like to get good data on all of the panes, but im just running with what I have at the mo.

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PhotoGav

PhotoGav

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Just now, Uranium235 said:

Its from the Star71, and 10x600 per pane but a couple only have an hours worth of subs... and its of mixed quality, I'd like to get good data on all of the panes, but im just running with what I have at the mo.

Thank you. Excellent work and refreshing to see the wide angle lens being applied to Galaxy Season. Makes me reconsider some of my imaging list choices.

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Uranium235

Uranium235

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18 minutes ago, ollypenrice said:

Good stuff. If it would be any help on field curvature I could give you Markarian's Chain and the circle of galaxies to its left taken in a single frame with the FSQ and full frame Kodak chip.

Olly

Thanks Olly, I will be in touch when I've got the final set of data. I'm half hoping you could also run it through Pixinsight to annote it as well ;)

For now, four of the panes snapped together alright but two of them required the intervention of registar. All I did was register the errant panes against what was already stitched together, and they seemed to fit alright(ish) after that - but theres no telling what will happen once I increase the overall size of the image.

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Uranium235

Uranium235

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6 minutes ago, Pompey Monkey said:

Well done.

 

I've given up on the Chain for this year as my second hand Star 71 is faulty: the Ha image of the Jelly I posted a while back masked the effect, but any LRGB subs have the coma like stars in one corner. Buyer beware! :(

You probably need to fiddle with the tilt adjuster then, but only by a tiny amount. The best way that I can think of would be to focus so you have three good corners, then pop a b-mask on - slew the focusing star to the affected corner, then adjust until the diffraction pattern says its in focus. But like I said, it will be a tiny adjustment. Possibly easier with a dslr too since its easier to figure out which corner belongs to what part of the focuser (ive found that CCDs can flip or mirror the image).

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Pompey Monkey

Pompey Monkey

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29 minutes ago, Uranium235 said:

You probably need to fiddle with the tilt adjuster then, but only by a tiny amount. The best way that I can think of would be to focus so you have three good corners, then pop a b-mask on - slew the focusing star to the affected corner, then adjust until the diffraction pattern says its in focus. But like I said, it will be a tiny adjustment. Possibly easier with a dslr too since its easier to figure out which corner belongs to what part of the focuser (ive found that CCDs can flip or mirror the image).

Hmm - the DSLR T-piece has an M48 thread doesn't it? That's a good idea :) 

As for the tilt adjuster, I tried the micro adjustments (1/8 of a turn at a time) with no apparent effect. As an experiment I tried a gross adjustment (1 1/2 turns) and I got the centre of the field in focus and both sides out of focus but the stars were still distorted in the same direction in the one corner. 

I haven't tried the trick with the mask yet though. I'l have a go next time it's clear with the mask and DSLR. I'll have to be very careful not to rotate the tilt adjuster afterwards though! ;)

If it's cloudy, I think I will start a new thread when I get home from work this evening with some images from the aberration inspector in PI.

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ollypenrice

ollypenrice

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8 hours ago, Uranium235 said:

Thanks Olly, I will be in touch when I've got the final set of data. I'm half hoping you could also run it through Pixinsight to annote it as well ;)

For now, four of the panes snapped together alright but two of them required the intervention of registar. All I did was register the errant panes against what was already stitched together, and they seemed to fit alright(ish) after that - but theres no telling what will happen once I increase the overall size of the image.

I always start with a middle panel in Registar and work outwards but multiple panel mosaics benefit from a template. I once had some success by using a screen grab from a planetarium with all the text etc removed. I resized this to the final size of the projected mosaic and tried to register panels to that. It worked for some of them. I need to do a bit more work on this.

Regarding the Star tilt adjuster, do you know of a source of instruction for it? I have a guest here at the moment who has one but can't find any manual.

Olly

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Pompey Monkey

Pompey Monkey

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3 hours ago, ollypenrice said:

 

I always start with a middle panel in Registar and work outwards but multiple panel mosaics benefit from a template. I once had some success by using a screen grab from a planetarium with all the text etc removed. I resized this to the final size of the projected mosaic and tried to register panels to that. It worked for some of them. I need to do a bit more work on this.

Regarding the Star tilt adjuster, do you know of a source of instruction for it? I have a guest here at the moment who has one but can't find any manual.

Olly

My Altair Astro version is simply three pairs of push-pull screws acting on a pair of plates. Slacken the puller and do up the pusher or vice-versa. A large adjustment to start with will help identify which screw pair corresponds to which part of the image.

To start, make sure that it is all reset i.e. the two plates touching, the pullers done up and the pushers just touching the other plate. That way you'l know that you are making an actual adjustment rather than just taking up slack.

Adjustments of 1/8 of a turn make quite a difference :)

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Uranium235

Uranium235

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4 hours ago, ollypenrice said:

 

I always start with a middle panel in Registar and work outwards but multiple panel mosaics benefit from a template. I once had some success by using a screen grab from a planetarium with all the text etc removed. I resized this to the final size of the projected mosaic and tried to register panels to that. It worked for some of them. I need to do a bit more work on this.

Regarding the Star tilt adjuster, do you know of a source of instruction for it? I have a guest here at the moment who has one but can't find any manual.

Olly

I tried the planetarium trick with Stellarium, but it didnt do a very good job - it probably needs more reference stars to work from.

But in regard to the tilt adjustment, Its pretty much the same here - Ive found no instruction on it so its going to be a case of "suck it and see". Perhaps later on tonight I will try building a basic artificial star using an LED torch, bung it at the end of the garden and see if I can get a diffraction pattern from a b-mask. If I can get that to work, I will post up what I did so it can help others out who have the odd dodgy corner. I would try a ball bearing, but thats not something I have to hand at the mo. Fortunately the short focal length of the 71 wont require a tiny hole, maybe just a small pinhole will do.

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