ollypenrice

One of our robotic scope owners has just installed a large format Moravian and it looks very convincing.

Olly

What happens if you take a first and a last sub from a run and then align them on the stars and combine them? The stars wll align but what about the frames of the two images? If those don't align then that's because of your PA. I'm wary of the claimed PA measurements offered by the various software packages because I've seen good reason to doubt them, using the test I describe.

Olly

22 minutes ago, ecuador said:

Eh, I assume you haven't tried the "Wipe" module? I had first tried the DBE module of PI (trial) and loved it (coming from Photoshop). When I switched to StarTools with its wipe module, DBE actually felt like a chore

As I said, I'm not aware of anything to beat DBE. That means what it says - I'm not aware of it. I don't claim that it doesn't exist! I'm not in the business of trying every new bit of software that appears on the market and I suppose that I'm mainly motivated to try new software when I see an image that breaks new ground. If I think, 'How did he or she do that?' then I'll be in there, full of curiosity. I'm hardly a PI evangelist, I'm manly a Ps imager, but DBE is profoundly impressive. If you have an alternative, tell us about it. Give us some demos. I'm all ears, I promise. If there is something out there which is more sophisticated than DBE - great.

Olly

Just think about what your imaging hardware costs. It's a lot. Now think abut how much of the final image quality comes from processing. It's also a lot! It's more than a lot, it's going to be something like 80%. You can't process rubbish so the hardware is very important, but a good capture is no more than the collection of good raw data. You still have to do something with it. My captures are no better now than they were ten years ago but my processing is a lot better.

DBE in Pixinsight has no rival of which I'm aware. I still think the software giants are PI and Ps. Look at the images 'out there' which you like the most and see how they were processed.

Olly

I don't think there is much doubt amongst historians that Hooke did have a role in giving Newton a cenceptual, though not a mathematical, leg up on his way to his theory of gravitation.

Of course Newton would never admit this. When Newton said he had seen further because he stood upon the shoulders of giants he was, in fact, taking a swipe at Hooke who was deformed and dwarfish. There's a geat Hooke biography byu Stephen Inwood which I have read and another by Allan Chpman which I have yet to read.

Olly

No point in my repeating my enthusiasm for this mount. Hope you're as happy, Harry (and Steve.)

Olly

I have to say that it looks very like PA to me. On what basis do you say that PA seems good? The simplest test is to take a 'first' image and a 'last' and combine them, then look at the edges of the frames. Any disparity in the alignment of frames, assuming reasonably round stars, comes from PA. 

Olly

An unusual look and feel to this one. Sh2 126, 2 panel HaLRGB, twin Takashashi FSQ106/fill frame CCD, Mesu 200.

The 'Breaking Wave' extension around Gamma Cass, down to the Pacman. 3 panel, twin Taks.

NGC 2170 using twin Tak and TEC 140 data. 35 hours.

Beverly Hills here we come. A joint effort with Mr and Mrs Gnomus. HaOIIILRGB, 35 hours.

And finally IC447, LRGB TEC 140. An eleven hour quickie!

As ever, the kit is co-owned by myself, Tom O'Donoghue and Yves Van den Broek. Thanks guys and guests, a good year.

Olly

The speed of the system is not linked absolutely to the F ratio rule in AP when using reducers. If you are interested in everything that fills the frame then the rule applies in useful way. If your real target is a small discrete object framed by dark sky which doesn't interest you, then the F ratio rule does not apply. (It becomes the F ratio myth.) The photographic F ratio rule is predicated upon varying the aperture.  A focal reducer leaves the aperture where it was and alters the focal length, so it brings in no new light from the discrete object. The two situations are entirely different.

I wonder what the effect of binning really is on this CMOS camera. From what I've read it may bring no increase in signal to noise, in which case why bin at all? More homework needed! I like many aspects of the camera so I'd better get studying.

Olly

51 minutes ago, glowingturnip said:

blimey, i'm being quoted from over two and a half years ago !  :-)

Sorry, I hadn't noticed the dates - but I've had worse!!

lly

Imagine what would happen if they put Robert Hooke on the pound coin while they were about it...

Oo-er missus.

Olly

1 hour ago, Astrosurf said:

Hi Olly, sorry to butt in. How do you do this? If my guiding goes wrong, it's nearly always the Dec!

Alexxx

Firstly you need to be slightly misaligned. I've never actually set out to misalign, I've just exploited the misalignment that was there already! (By not endlessly refining the PA but settling for a 'close enough' alignment.) You then disable the guiding in Dec on one axis and see if that's the axis you do or don't need to guide on. If the mount guides in Dec that's fine. If it drifts off target you need to re-activate the direction you disabled and disable the other one. Write down the result of this test (if you're anything like me...) and reverse the disabling after the meridian flip.

Olly

It's good to see Takahashi doing something about the issue. Hope you get sorted.

Olly

On 20/05/2014 at 17:48, glowingturnip said:

i like the theory that a slight mis-align means that your guiding doesn't keep switching on dec - sounds like an excuse for me to be lazy  ;-)

It's very well known and certainly not my idea. I find it works, though.

In saying that if some subs are good and some not it cannot be PA, I should have added 'while imaging the same target.' 

Olly

2 hours ago, Ant said:

iPhone 5s, 22 degree halo

Has to be the winner!

lly

13 minutes ago, barkis said:

HehHeh!  Are you kidding Olly?   I bet Monique and you have one apiece . 

Not a bit of it, Ron! I had my first mobile only about a year ago and it's a flip phone designed for grandmas, according to the sales person who dealt with me. I can never find it, hate being cluttered up with it and can never remember the number when people ask. I dont 'txt'  under any circumstances. I consider the thing to be one step up the food chain from rap music...

lly

Smartphone? What's that? 

Olly

30 minutes ago, martin_h said:

Yep that sums it up, I only align my camera by slewing in RA during an exposure, and have never adjusted for cone error(life is to short). Close enough for jazz is my philosophy!

Mine too, though I don't get much rotation so far as I'm aware.

Olly

Given that it took over 200 years of telescopic astronomy to find the stellar parallax on a baseline of two astronomical units or nearly 200 million miles I think we can safely dispense with the idea that it arises from the distance between one side of Rob's pier and the other.  We all know that he's a stickler for fine resolution but... 

If there were neither cone error nor non-orthogonality then surely the images would have to align perfectly.

So what can it be? Non orthogonality of the camera? When the mount flips, any difference between camera angle and lines of RA and Dec will turn into twice that angle of difference between the image before and the image after.

Also, when we align our cameras along RA and Dec, by slewing them while exposing, we are doing so with any cone error already in place, so that cone error is factored into our alignment. Now surely this error we have factored in is 'sided.' That is, it matters which side of the mount we are on when we carry out the procedure. Again, any error will be doubled when measured as a comparison between 'before' and 'after' images. And to take this a step further, won't the cone error we have factored into our camera angle be local to the area of the sky in which we carried it out?

In a nutshell there is a complex and interactive relationship between cone error and camera angle.

Olly

Yes I know, I'm a dinosaur - but all this 'stuff' can (and often does) eat up a perfectly good night's imaging. Software automation can be like kids and homework. They will spend more time and effort on finding ways not to do it theselves than it would have taken just to do it.

Now Springbank never did anybody any harm.*

Olly

*This is not a quotation from the BMA.

Humph, robotic focus. Any of you guys host five robotic scopes? I do, and I also host five fingers on each hand and they are not connected by USB....

lly

17 hours ago, mftoet said:

 

One of the many refractors + correctors, extenders and reducers of Borg / Astro Hutech might be the answer. I once owned a Borg 101ED that covered Medium Format. I used it with a Mamiya 645 camera. 

http://www.sciencecenter.net/hutech/borg/astrogr/index.htm

You can also keep an eye out for secondhand Pentax refractors from the analogue age. Remember that "full frame" (35mm) coverage was the standard back then. 

But perhaps the problem with the older scopes can be the blue correction, which didn't need to be anything like as good at the shortest wavelengths as is now needed for digital cameras? My Mk 1 F5 Genesis (remember that one?) was Tak-like in narrowband but out of its depth in blue.

Olly

1 hour ago, kirkster501 said:

Gnomus (I would have used Steve, but there's too many of us about on this thread ),

The pixel size of that image is such because it is just a screen capture - yes, as you state,  the original is 2800x2200.  Even in that image the stars to the upper left are not 100% correct.  But I think that can be explained by the fact these were 6 x 300s exposures and my PA is not perfect.

I've attached a single M31 300s luminance with the 85 + reducer that has not been tinkered with in any way.  I cannot see anything wrong with my scope.  At extreme zoomed in maybe the tiniest amount of egginess in the corners.  I am prepared to accept that even if it were the scope producing it. So I am happy with my BabyQ.  Sad that some folks have been disappointed with theirs and the dream did not live up to expectations.  Indeed, there is £4000 worth of scope when the reducer is factored in.  At that price one has a right to expect perfection.

You'll struggle to find a scope that can do better at F3.9 than that. Top left isn't perfect but it isn't bad and you can write a quick Ps action for 'rounding stars' (one at a time but there won't be many) to fix that corner. Mind you, if you were using an 8300 chip you might not be so happy... While it ought to be possible to buy a scope knowing that it will give perfect stars corner to corner within the specified image circle it just seems that you can't!

One thing, though Steve (Kirk!): put the official flattener on your TEC and there you will have a flat field you could land a glider on. WIth full frame ours isn't even slightly taxed. 

Olly

1 hour ago, gnomus said:

So with the demise of the WO Star 71 (which had pretty poor QC in any case, it would seem), and a bar on Tak, what options are out there for the aspiring widefield imager wanting something a little better (or maybe a whole lot better) quality than an ED80?  By widefield, I mean it would need to be able to fit in M31 in a 'oner'.  

The Esprit 80 looks a good option, but it is on a fixed foot that, I am told, cannot be removed.  It is not clear, therefore, how you can get a guidescope on top of it, unless you are happy with a finderscope sitting in the standard Synta shoe (I'm not sure that I am).  

I feel a new thread coming on........  (You can tell the weather is rubbish in blighty at the moment can't you?)

It's a serious question!

I don't think you can get M31 in a single frame with anything resembling a telescopic focal length. If you get the full outer glow it is a two panel in full frame format at 500mm FL. That means you have to have something that will cover full frame to get anywhere near, in one. The claimed image circle for the Esprit 80 with flattener is a rather paltry 33mm so that won't take a big chip. For the big Kodaks you need about 45 or 46. Theory says 44 but that turns out to be a bit 'iffy.'

It was after some thought that we went for the older fluorite FSQ106N option here. The 88mm claimed circle rather puts the problem to bed. Buying second hand you can ask for a sample image from the scope, too.

It shouldn't be this difficult but it is...

Olly

Besides the two Steves on here I have come across several other problem Baby Q posts, all about corner stars. Mine was fine and there's one here in our robotic shed which is also fine but I no longer recommend the Baby Q when asked because there are too many bad ones circulating. When you can't trust the European importer (and you can't, as Steve's experience shows) or the QC then it's time to take a rain check. The clincher in Steve's case came when he found the same camera perfectly satisfactory in a later scope, so it wasn't chip tilt. In an all-screwed assembly that's about that, surely?

We now run a pair of old FSQ106Ns here and are 100% happy wth them. 

Olly