ollypenrice

Geweldig mooie plaat! Jullie hebben een fantastische prestatie geleverd! I assume you understand some Dutch by now; the "G-s" and "Ch" are pronounced like the G in Gouda - like a choking sound - which I've heard you pronounce so well. ;-)

Thanks Maurice. If I'm not mistaken that means, My hovercraft is full of eels.  In trying to eat them all my choking sounds are getting better!

lly

PS Dutch is not listed in Google Translate. You need to complain!

how did you process this? i know you like using PS but this does have a PI feel to it

AAAARRRRGGHHH!!!!!!!!!  A mortal wound!   

Only joking.

All panels preprocessed in Astro Art 5 using flats, bias-used-as-dark and Bad Pixel Map.

ABE or DBE used to de-gradient the linear stacks in Pixinsight.

Individual panels from different cameras combined in Registar then co-registered to a master widefield template but not combined in Registar.

Images paritially stretched in Ps and then combined by eye using Ps tools to balance the brightnesses for a seamless blend.

At this point Tom and I will have done our own thing. What I did here was my own final stretch of the three images, ie L, RGB and Ha. Tom has more PC power than I so I could only do certain things to the whole image. I generally had to break it down into four or five sections and do the same thing to each. (Even just doing a 'Save As' took a couple of minutes...)

L was added to RGB conventionally enough in Ps using interations, boosting the RGB saturation under a partial L application, smoothing then re-applying till L was at full opacity with enough colour to fill it.

Ha was added to red in blend mode lighten. The application was rather thuggish! That's to say, to bring the Ha into play against the strong red layer I had to give it a massive contrast (S shaped) curve while it was in situ over the red channel. By doing this I could keep the low Ha signal below the red (to stop the entire sky turning red) while allowing the brighter Ha signal to lift the reds for the Loop and Meissa nebulosity, etc.

Images I already had from the TEC140 at higher resolution (Horse, Flame, M42, Running Man and M78 were taken 'as is' in finished form and registered/resized to the mosaic in Registar. They were then blended in using Ps, with adjustments to levels and colour balance as necessary and very much by eye.

Challenges included getting the overall colour balance consistent (Selective Colour in Ps) and keeping the seven big stars down. This was done using Layers and multiple stretches in Ps and took a long time. (Half a day on Rigel, for instance...) It's easy enough to get a small Rigel but not to get a small Rigel without a dark shadow around it. That took longer! (The final size of the seven bright stars is a matter of taste, though I noted their magnitudes and respected that as best I could. I felt they needed to be big enough to show the Orion shape but splitting Alnitak was a matter of professional pride so that set an upper limit on all seven!  )

So, Astro Art, Registar, Pixinsight (vital for DBE/ABE) and mostly Ps. (I'm a Layer-oholic.)

Olly

I think we're both knocked out by the kindness of these comments. Many many thanks.

Olly

There is nothing inexpensive about Deep Sky astrophotography regrettably. I shelled out over £2500 - my performance bonus paid in June - for my CCD and filter wheel/filters. I have nigh on £5k worth of gear now. And still not got all what I need. You can easily double or triple that sum for top range gear like a Takahashi scope and Mesu mount with a Atik 11000 - all stuff Olly has btw !

Don't give up on a DSLR. You can get fabulous results with one. Best beginner combination to get good resultsfor DSO AP is a ED80/HEQ5 and a modded DSLR. You can pick that lot up for a grand or so and will get you going.

Yes but I've got an excuse! I earn my living with it...

OK, I never said it was a good excuse!   

What I would say, though, is that in a vote for best optics for buck I think I'd have to go for the subject of this thread, the 6 inch RC. Or the 8 inch. John and Sara really do show what's possible. The resolution on that Pacman above is astounding.

Olly

I hesitate to post again on this but... ...I agree Astrodon and QSI are in agreement. What they are saying is consistent with the diagram I posted. That is adding a filter pushes the focus out by ~ 1/3 thckness i.e. 1mm for a 3mm filter. This means that camera plus filter consumes 1mm less of geometric backfocus than the camera alone. 

What to do if you have a corrector/reducer depends on if you want to maintain the geometric distance or the optical distance. 

If you want to maintain the geometric distance add 1mm as John proposes if you want to maintain the optical distance subtract 1mm and refocus. 

Given that CCD will have a window and cover plate then the optical distance is probably ill defined anyway!

I now retire from this thread.

Regards Andrew

Retire at will, Andrew, as is your perfect right, but please don't do so before accepting my heartfelt thanks for the most edifying of posts! I must admit to functioning at about 15% of an already limited mental capacity following an accident which leaves me unable to sit in comfort for more than a few minutes, so my mind is not really on the task. I'll go through all this in a month or so when I'm back to what passes for normal!

Olly

OK, it's the class Dunce again! Why wouldn't Andrew's ray diagram apply to a reducer? I don't understand why a reducer produces a beam different from the one produced by the objective.

Olly

Although I don't use his filters, here's a quote from Don Goldman (Astrodon) who I believe knows a thing or two about filters but maybe hasn't got the price right yet! :-

You are quite mistaken Mr Wolf. My husband has the prices absolutely right.

Mrs Goldman.

I agree, Olly, the difference is well within the acceptable tolerance but, one them is right and one of them is wrong and the difference between the two is TWICE the change in light path length!

I see both arguments which is why I find this such an intriguing discussion!

I was meaning no purely physical increase but I have now returned to my original belief that there must be an optical increase.

Indeed, most intriguing. I'm glad I don't need an LP filter as well!

Olly

Merlin66's argument is compelling (see what I mean about great arguments out there!!). This would seem to confirm the QSI and Optcorp stance but if the light path has now been modified, how relevant is the original 50mm PHYSICAL spacing in the example above?

Fascinating stuff.......

Sent from my iPhone from somewhere dark .....

In reality there will usually be no physical increase in the distance brought about by inserting a filter because the 'increase' is contained with the thickness allowed for the filterwheel. Yes? No?? Arrrgh.

Olly

I agree entirely with Andrew S's ray diagram and this is what made me say that I can't understand the subtraction claims. It's exactly the ray diagram I originally had in my head.  It's just that when QSI say the reverse I feel outgunned. Now that Don Goldman agrees with the ray diagram I'm delighted. I've emailed my favourite optical engineer and am awaiting a reply.

This is a rum situation!

Olly

This is my understanding too.

Steve, if I do the ray diagram I can't see how it can be the opposite but both QSI and Optcorp say that it is. When Optcorp specified my extender for the TEC flattener they subtracted I/3 of the filter's glass thickness from the system FL. This is also what QSI say on the link above. I hate doing things by rote without understanding them but, sheep-like, I now follow the subtraction rule without knowing why.

I must say that the Optcorp extender has worked perfectly on the TEC flattener with exacting full frame chip, but this doesn't prove that they were right. I think I need to write to Ralf, the font of optical knowledge... 

so its nothing to do with chip distance to flattner , just focus ??

edit to last post , I am a few thu over not under 55mm

No, it applies to chip distance if we are talking about an add-on flattener that moves with the drawtube. It can be entirely ignored in inherently flat field instruments like Petzvals where all it will do is crop a mm off your backfocus. This shouldn't be tight enough to be affected.

Olly

I didn't recognize you by your forum name, almcl! Sorry about that.

Steve has it with Alnilam, I suspect. I gave the area a quick eyeball on a widefield and decided it didn't line up as a likely candidate but I hadn't allowed for the orientation of your camera. In doing it properly Steve has fingered the suspect's collar, I'd say.

Just in terms of good practice you have no flocking in the tube and you also have a couple of bolt intrusions into what might be the lightpath. SInce the tube also has a raised seam I might be inclined to flock it and trim the finder bolts. I've no idea whether this might be a player. I do have a big visual Newt, as you know, but imaging is far more exacting in terms of things having to be right.

Best,

Olly

Edit, I'd maybe blacken the vanes as well. Matt paints using pigments are best since dye based paints can reflect IR, it seems. Barbecue paints use pigments.

I think it is probably a reflection from the vane.

You also need to give the vanes some attention, I think. I'm not well up on Newts but how good is your coillimation and is there a twist in the vane?

Olly

As has already been suggested, guiding in only the one necessary direction in Dec (experiment to find which that is) is an excellent cure for oscillation. Being slighty misaligned is a positive advantage in this situation, but not enough to give rotation.

Olly

David Lukehust uses them, as indeed do Obsession, so that probably says it's a good idea.

Olly

How do you avoid diffraction spikes when observing planets with a newt, i guess you just get the planet "of axis", between the spider vanes?

All of the aperture contributes to all of the image so you can't locate the planet between the vanes!

The only solution (and a very good one) is to use a curved spider along these lines. http://www.rfroyce.com/spider_cv_8/spider.htm

WHat happens here is that each segment of the corve produces a diffraction artifact in a different place.

Olly

lol yeah

For a moment I thought he was actually going to give one a go!

Hehheh, be fair, I've backed these little Newt images from the start. You don't have any choice, they are excellent. They really are.

I'm in a slightly different position in that I'm a provider, sometimes running around like a blue-posteriored fly and even with 'plug and play' I sometimes can't get it all working in time, so adding collimation tasks is not on my to do list. But, hats off, I think that bang for imaging buck I doubt that the 130 can be beaten.

Olly

While I've been knocked out by Uranium's images for some time, and said so, I've missed this thread.

I don't see anything remotely 'entry level' about the best images posted here. If you want to image at this kind of focal length on a medium to small chip then this telescope clearly has a lot going for it. I think it will take on, quite literally, all comers at any price. It is fast enough to be fast but not so fast as to invite exasperating complications that will rob the imager of many good nights. In refractor terms it has a fair bit of aperture. Apart from the coma corrector it is inherently apochromatic - totally so.

What do you get with a car-priced Takahashi FSQ that you don't get with this scope? A vast flatfield circle which you only need with a big chip. Freedom from collimation. No diffraction spikes. These are not nothing, but, yikes, they come at a price...

Olly

I have one of these as well, and a Pronto. I prefer the Pronto, personally, but it is heavier. However, I don't find the 66 focuser to be capable of carrying much. It was fine with a small CCD and manual filterwheel but would have no hope of holding my present CCD gear. That said, it couldn't cover a large chip so nobody would ask it to do so. It does give a nice visual image and is incredibly competent as a narrowband imaging scope on chips which it can cover. To be honest it isn't far behind a Baby Q in narrowband and with a small chip. Imaging in broadband does show its limitations, though. Stars are far bigger and less controlled than with the premium stuff, but what do you expect? I think it does well.

Since this review it might be worth noting that the little TS Quad has, it seems, had its pinched optics cured.

I'm not sure that I'd call my ZS66 a keeper but, then again, I've kept it and have no plans to sell it, so I guess maybe it is! I also started imaging with it so it has some sentimental value. I'll put one of my early attempts below. Atik 16HR, 13Nm Ha filter.

Olly

Julian, do you know how Shapely calibrated the Cepheid distance, though? This bit seems to be glossed over in most of the histories.

Olly

Yes. (By the way, stars are measured in Watts with a lot of zeros begind the first digit!)

Do you know the HR diagram? It Googles. Stars can be placed on the diagram using thier spectra to identify them and then an absolute magnitude (true intrinsic brightness) can be read off on the left hand side. When compared with the distance-affected apparent magnitude this yields an approximate distance.

Type 1a supernovae are good bright candles. They should all be similar because they go Pop when the accreting star reaches 1.6 solar masses.

Olly

Once beyond parallax we often rely on the idea that there is a difference between how bright something really is and how bright it appears to us at the distance it is from us.

If we have a 100 watt lightbulb its hundred watts will be radiated out in all directions (ignoring the brass bit that sticks in the holder!) If we are a metre away we can imagine a spherical shell with a 1 metre radius. That 1 metre shell has, in total, 100 watts worth of light at its imaginary surface. If we move to a distance of 2 metres and imagine a spherical shell around the bulb, the surface of that shell is now 4x larger and the 100 watts are now spread 4x thinner over that surface. So the apparent brightness of the bulb goes down as the inverse square of its distance. Now say we are 100 metes away and we have a photometer with a 1 square metre detector and this measures a certain (small) amount of  light flux from the new shell. From this we can calculate the total surface area of the shell and so its radius, which is the distance we were looking for.

How do we know the true wattage of a star or a galaxy? Partly from measuremnt of known examples, partly from astrophysics and a knowledge of nuclear energy. Certain types of object are considered 'standard candles.' They should give off a pretty standard wattage so how bright they appear gives an idea of how far away they are.

An amateur's answer while waiting for the pros.

Olly

This is a great thread. Very interesting. Thanks for the detailed account.

Olly

I host one at my place, though it isn't mine. It's a pretty good idea.

Olly