SilverAstro

DSS can not compensate for those parts of the sky that have rotated out of the camera frame during the 2nd and 3rd hours

Ah ! what we need are circular sensors !! doh

11 minutes ago, Nigel G said:

Here's one with slight frame rotation

Hehee ! Nice one , yep just a little ! 

Shame about the clouds

5 minutes ago, jimbo747 said:

The image has rotated quite a bit in between taking the first frame and the last, presumably because of its position in the sky,

Thanks for those, I'll have a think about them, (the middle one is well rotated by 90deg but I guess that it a software/posting glitch !? )

cos I was imagining a streak due to the 'frame rotation' due to the nature of an alt-az mount that it would appear to be like a bull's-eye display, the object in the middle with a set of arc stars round it getting bigger the further out. ( Like a star trails picture round Polaris in fact ! )

1 minute ago, The Admiral said:

Ha ha, yes!

and it is real difficult thinking it / typing it  without being able to wave one's arms about well, I can, but you lot cant see !!!

I think I need a beer , , ,

21 minutes ago, SteveNickolls said:

Hi,

Thanks for your kind comments. They would both have been subject to some cropping, the one taken with the Canon piggybacked would only have been cropped slightly a few pixels around the edge. The piggybacked image was taken at 200mm FL (on a APS-C camera like the Canon 600D I think this works out at 320mm) while the other was through my refractor (500mm FL). The image through the telescope was cropped more vertically to remove a lot of poorer background. hope that helps.

Cheers,
Steve

The reason for the question was this business of the proportion of streak*, it being a degree of rotation, which in the meanwhile of my domestic you are all talking about Cos I was trying to get my head round -> if they are similar scales or maybe even if they are not, the proportion of any streak due (*edit as Ian has just said !)  should be the same and thus not the reason for DSS accepting the one lot compared to the other lot.

and on top of all that they are both taken on the same alt-az mount so it cant be drive jitter sooooo I'm not sure where to go next with  it !

* I like streak, easier to type than "field rot "

1 hour ago, The Admiral said:

My emphasis. Why rotate in software, why not rotate the camera at the beginning of each set so that you get back to roughly the same starting position for each set? Presumably DSS would stack them all as one set?

You may need to do flats for each position if the field uniformity is not axially symmetric, in which case I guess you'd need to stack each set separately.

Ian

Indeed ! that is the thought that I was having that caused me to put in the > Edit : hold !!

that if one did not re-align the camera with the scope (and/or celestial sphere) then it would still be limited to the 'common circle view' that was causing the Nigel crop, so I went away to have a think, ,  and then domestic got in the way So if two of us thunk it it must be right

Any moment now we'll be back to de-rotating mechanisms !

23 minutes ago, Gina said:

have at last found why

I am sooooo pleased to hear that !

It was giving me nightmares thinking of all those luvverly subs going awol, now I can get on with the rest of my life LOL ! 

26 minutes ago, jimbo747 said:

Now the image isn't anything special, but the reason I post is interestingly, most (90%) of the images when the object was high in the sky showed star streaks, however

I cant see it !

You are right, I cant see frame rotation, interesting !

Perhaps you could post a streaky one because I dont think I have seen a picture of this frame rotation wot everyone is on about   (people dont generally post their duds, but they can often be as informative, like what not to do ! as the good ones ) As you say, high in the south is supposed to be the poor direction, very interesting.

Nice dumbell, nice image.

1 hour ago, Nigel G said:

Field rotation over a long session will leave the final image to be cropped quite a considerable amount to reduce stacking artifacts.

Or divide one nights set into two or three batches, stack each, rotate each by hand in software of choice, and then stack the resulting two or three combo frames ? ? ( been there, Tshirts etc, also helps with jogged tripods )

Edit : put the above on "hold" I'll have to re-think that, it may not have been my problem, perhaps it was just lens distortion in my camera lens , , , or jogged tripods !  my head hurts

Hi Steve very interesting very nice images, amazing in fact

The two of Andromeda - are they full frames or cropped ? Reason I ask is, are the scales of the images as presented comparable ?

1 hour ago, Gina said:

 imaging rigs upside down   I'm far from sure that a triple 460EX imaging rig would do any better than one ZWO and filter wheel. 

Hmmm, but what about 460EX   3 x ASI1600 and then , , oh you  got there before me    hmmm, how does one quote two posts when the second one you want is on a different page , , , 

19 minutes ago, Gina said:

I have captured sets of Ha, OIII and SII but not yet processed them.  That was the 5nm Ha filter.  I'll probably repeat the Ha with the 3nm filter when I get the chance.

I've got a lot of data to process so plenty to do while the weather prevents imaging apart for many other things

Yes I remember, that will make for an interesting comparison.

Good job you are not (yet) into solar ! , , lots of sun data out there today as well 

14 hours ago, Gina said:

Decided to try out the 3nm Ha filter on the NAN and Pelican.

I'm quite tired out just reading you ! At this rate you are going to have to take on an assistant (or three!) ( (s)he could be using the other Ha filter on one of your other rigs )

How did you get on with / finish up on that Cygnus Loop marathon ? It is a beautiful object, not so 'in yer face' as the NAN ? !

@>"running at -25°C."  All the impressive sensitivity etc aside -  I'm am still amazed that these things can run at that sort of temp without turning into a block of ice !!

Watching with enormous interest , , ,

1 hour ago, Gina said:

Nearly finished the Cygnus Loop   IC1396 next I think.

A fine clear night

and I have taken another liberty with your pics Stars from the Ha +Ha,neb +the single O,neb (didnt notice the SII in time !) I wondered why I had lost a lot of red then realised it had turned into most of the yellow, I suppose that should happen ?

8 minutes ago, SilverAstro said:

Ancient physics reminds me of the Hydrogen Balmer(sp?)  series producing beta gamma &etc, I have seen discussion somewhere about a Hbeta filter,

54 minutes ago, Gina said:

labelled hydrogen alpha and beta -

Ooops, sorry, re-read and I see you have already found the Hb ! 

There is also an interesting hydrogen at 21cm - but a little outside these types of sensor lol !

31 minutes ago, Gina said:

I think I need to look into the DSS settings further - it's a complicated beastie 

The amount of the unwanted light either side of the wanted wavelength depends on the bandwidth. 

Don't know if there are other wavelengths for H and O.

Thanks for that explain ( and no I dont like sulfur neiver ) !

I had been thinking that the only wanted light was that of the nebula, but now you explain I suppose the 'unwanted' is light pollution and/or the moon. Yes I am seeing now I think. Ancient physics reminds me of the Hydrogen Balmer(sp?)  series producing beta gamma &etc, I have seen discussion somewhere about a Hbeta filter, but there was doubt if it was needed as it produced only the same hydrogen region image, something like that.

As for DSS yep, I know, a little mysterious at times , but I have only used it for simple stacks of camera&tripod pics. of lots of short exposures. It is throwing away 1/2 your life ! so you must beat it into submission !

Good luck with the usb.

2 hours ago, Gina said:

I'm going to try something - what happens if I try uploading the full size image of 4656×3520 pixels...  Please wait

Very nice ! ( and only 2min to download on my slow 3G, followed by 1.5min whilst my lappy untangled its VirtualMemory and returned control to me )

Shame about DSS not liking 50% of your subs, wonder why that is ?

Have you done any exposures in white/mono light and/or RG&B ? with it for comparison. Presumably the 5nm filter cuts out a lot / needs a lot longer exposure ( me never having done anything like this should probably ask that in the beginners section ! )  ie. in what way does the 5nm image differ from, for example, a broad band red as given by a moded dslr (apart from needed exposure duration and noise !? )

3 hours ago, Gina said:

OK - found it - virtual memory - used Windows Help   Size was 4055MB but system managed - help recommended custom size so I set it to 4096.

Sorry ! my bad, my age showing, they used to be swapfiles and pagefiles and things in days of yore !

So that isnt the problem then, I mean not mis-set silly big or silly small by some misfortune

3 hours ago, Gina said:

Drive C: is just 5% fragmented so I don't think that's the problem.  One thing might be lack of RAM - it's got just 4GB.

Agreed, not the prob then, as long as your Swapfile is on C ? Might it be on D ? but why has the m/c become slow, 4GB RAM wouldnt explain it unless it used to be somewhat bigger and evaporated !

and is your swapfile still the same size as you thought it was, oh and did it get defragged as well, to make sure you have a contiguous big one for max speed you need to , , , ask an expert cos it is a long time since I did this on mine !! something like make it small, then defrag, then make it large again ? or the other way round ?

Just a few random thoughts for your consideration, prob a load of old . . .  !

50 minutes ago, Gina said:

running Win 7 though the Pro version.  It's just getting slower and slower and doing anything intensive like Photoshop is getting to be a right pain.

Defragment recently ? Is it possible that the auto defragger has been turned off ?

I dunno Win7, but Vista has a built-in defragger that is normally enabled and runs in the background but it can be turned off ( like mine is, hmm that reminds me, I must do a defrag ! )

1 hour ago, Gina said:

 I'll reverse the image

I think the first one was the real one,  just that it was photographed from the other side and you are in fact an alien.  Now you are trying to pretend

That is a bit shocking ! A cheap low class supply may produce 21v off-load and drop to reg 13v on load. But I would not have expected that of a Maplin one ( or would I ? ! )

Did you measure that while it was supplying your mount, or open-ended ?  Have you something unimportant to hang on it to see ?

22 hours ago, Moonshane said:

Here's mine

Gosh yours is a big one,

mine's only little

Actually, my equipment used to be a 6" Newt and a camera on a tripod. But the Newt is retired ( nackered mirror coating after 50y, needs redoing but not worth the cost ?) and daughter has made off with the tripod, but give me a wee while and I may figure out how to get my camera to selfie hand-held in the dark !!

edit, ooops forgot to mention my binos.

21 hours ago, Peco4321 said:

with part of UM visible over the end of the scope.

Great pic ! I like the composition, "I've got my eye on you" or ( taking cue from your other posts ) " I've not got all the gear I want yet but I'm on my way"

How did you avoid star trail in 25sec ?

and that is an interesting part of UM, you split Mizar-Alcor pair !

1 hour ago, wxsatuser said:

Jerry Lodriguss has a nice article about modding.

http://www.astropix.com/HTML/I_ASTROP/DSLR_HA.HTM

An interesting read but I am bothered about his second NA pic., the 'mouse over' one. How can you get more red light by interposing a filter !

More contrast yes, but not more light which is what he seems to be implying?, and makes it look like, in that example.

However, he has committed a basic sin of comparative experiments (!), he has changed two variables at once, a ) inserted a filter and b ) changed the method of exposure. I would like to see that replicated by someone else.