ollypenrice

14 hours ago, Stub Mandrel said:

What do professional astronomers use?

But what do they use them for?

lly

4 hours ago, Piero said:

 

The weird thing in this sort of topics is the refusal of the simple fact that to see more one needs to capture more light, assuming that all the variables are optimised (sky, collimation, etc). 

 

...assuming all the variables are optimized. But are they?

I don't think anyone on this thread has argued against aperture - have they? I certainly haven't, and certainly wouldn't.

Imagers can capture more light by taking longer exposures. What they want is to see that light landing on their chips in the right place. 

Olly

1 minute ago, mikeDnight said:

SCT owners should be prosecuted under cruelty to photons act, which doesn't actually exist, but should do! After travelling hundreds of thousands or even millions of light years, only to end up bellyflopping onto a Schmidt corrector plate; its just so sad!!

Ooooohhhh, things are warming up.

To be fair, photons which have spent only a few minutes in flight from Jupiter probably feel they've hit the jackpot if they sail into Damian Peach's corrector plate! Immortality at a stroke...

Olly

2 hours ago, Stub Mandrel said:

Don't fret @ollypenrice, I've fixed it for you

(Alternative title: "What a Refractor Owner thinks Newtonian Users see")

Thanks, that's so much better. I'll give you a free week's holiday if you tell me how you did it.*

Olly

*In Anchorage, Alaska in June.

2 hours ago, estwing said:

Last time I observed with the Frac pack this happened...

 

It was a really warm night and he was trying to get it to ambient.

Olly

4 minutes ago, iPeace said:

Oh, shush and behave.

Wot, on a refractor versus reflector thread? Nobody behaves on those. Especially those reflector crackpots! 

Olly

PS For anyone suffering from chronic sense of humour failure, this was a joke. Not really!!!! 

6 hours ago, F15Rules said:

"Looking THROUGH them??"

I thought Tak owners only looked AT them..at EVERY  opportunity!!! 

Dave

I really don't. Mine's a scruffy old thing with a home made tangent arm microfocuser and a handwritten sticker on it to remind me which one it is on the dual rig I share with Tom. I did clean it once when Steve Richards was about to drop in! 

7 hours ago, vlaiv said:

Interestingly enough, most of the people in this thread while standing up in defense of refracting telescope design (me included) did little to counter actual arguments presented in article.

Most of the things listed in article are in fact true. I think that it would be in best interest of OP and general community that participants of this discussion either state exact disagreement with particular point made in article, or provide alternative view to why refractors are indeed good (particular use case or even personal preference).

I would not focus my attention to author either, everyone has a right to voice their opinion and their particular style might not suit us well, but we should be able to distinguish their preferences / views to actual claims (which we can subject to counter argument).

I posted a refractor image which I wanted to speak for itself. To speak for it instead I would say this: in a Newtonian image of this target there would be little there apart from diffraction spikes! And if I tried it in an SCT it would need a six panel mosaic - and there would be no hope of holding down the stars which tend to be pretty soft in SCTs. This was taken in a small (but expensive) 3 inch refractor, smaller and more compact than an SCT and much easier to mount and guide.

If all you are interested in, visually, is going deeper then aperture is king. But if all you are interested in is going deeper then get a bigger scope. Visual refractor enthusiasts are not obsessed with going deeper, they are are passionate about the quality of the view at an emotional level. Deeper or better? There is no right answer. Both are perfectly valid obsessions.

I've no axe to grind. As a provider I have refractors, Newts and SCTs here and I like them all. Well, I like them all visually but for imaging I really like refractors.  

Olly

One thing does bug me about refractors, though. Try as I might I can't see those spikes sticking out of stars.

Olly

The last thing in the world that I'd do to a working scope would be to update the software. Your efforts so far tell you one thing for sure - the update software doesn't work! I'd keep well away from it.

Olly

What do I think of the article?

Olly

This has that 'just right' look about it!

Olly

IC348 and friends imaged with Mr and Mrs Gnomus and with the participation of Tom O'Donoghue. HaLRGB.

The large, faint IC342 with an inset showing M101 at the same scale.

A head-banging attempt to find the tidal loops around the Sunflower in the TEC140. When I learn more about inverse masking I'll try to improve this!

And finally two 'improvers' where substantial new amounts of data have helped older images. M42 is LRGB. The Rosette is HaOIIILRGB.

Olly

I must say that I usually use luminance flats for all filters and that they work fine. If, on occasion, they don't I shoot flats per filter - but this is exceptional.

I don't follow Vliav's procedure at all, but that's with CCD, set point cooled. I use a master bias as a dark and a master bias as a flat-dark. I use a defect map as well and an aggressive hot pixel filter when stacking. For me this works better than the standard dark subtraction routine. Much better, in fact. So all I can usefully suggest is that you experiment to see what works best for you. Don't get hung up on the theory. You won't be posting the theory on the imaging boards.

Olly

On 1/30/2018 at 18:51, kirkster501 said:

Thanks, I will check into that.  Another theory is that I have done much of my tinkering in rubbish skies.  Last night was a quite misty and murky and not an AP night at all and I was playing with the OAG, hence this issue.  Could the fading in and out of the "double" star be atmospheric in some strange way?  I need a clear, reasonable night to test this.

I doubt it, personally. You have two crisp stellar images in the screen grab you posted. Murky nights produce soft fuzzy stars, not pairs of crisp doubles, and faint ones tend just to disappear. This is certainly a new one on me. Is the turret of your OAG absolutely rigid? It couldn't have the ability to rock slightly? We had this once with an older model SX OAG and I made a steel strap to stop it.

The thing is that whatever is happening in your setup is happening quickly because both the real and the spurious stellar images are sharp.

Can we completely rule out hot pixels? Are you subtracting a dark as you guide in PHD2?

Olly

On 8/4/2012 at 16:44, knobby said:

Imagine the telescope is a funnel and you are using it to fill a bottle with water ... (please, please don't try this in reality) if your scope was short and wide the water would flow 'fast' ... if it was thin and long then the water would flow 'slow'

Substitute light for water and the bottle for your eye, bobs your uncle.

Very crude / basic analogy but it works on my kids

...but if it was wide and long the water would flow just as fast as it would in an equally wide short scope. And what does that bring us to? Oh no, it brings us with perfect precision to the F ratio myth!

Olly

1 hour ago, swag72 said:

For me the question would be..... will the Tak 106 increase the quality of your images over the Esprit? Personally I would suggest not. The big thing going for the 106 of course is it's massive imaging circle. You'd never have to worry about not being able to get a bigger chipped camera..... but with that change invokes new BIG filters and that's a pretty expensive pill to swallow.

If you want to waste money then a Tak 106 (the new kind!) ... if you want value for money then the Esprit range. If I didn't have the FSQ85's then I'd be buying the Esprit for sure. It makes so much sense.

1 hour ago, PhotoGav said:

 

@swag72 - absolutely, that is why I had eliminated the Tak, until the French Devil re-opened that argument!!

 

 Awe, I'm only advocating a second hand 106N and agree with Sara that the only reason for going for a new FSQ would be for the big chip it can cover! Tak have also blotted their QC copybook rather badly of late.

I, too, like the Esprits and would be happy to have one.

Olly

11 hours ago, PhotoGav said:

Thank you John, do you use the dedicated flattener?

Thank you Olly, that’s what I fear. You have just reintroduced the earlier eliminated FSQ106 and potentially a large dent in my Astro budget (I was thinking that a ‘cheaper scope’ would enable a filter upgrade)! I have seen the occasional second hand one, but generally around £3k. The most recent was in Rome, which makes viewing and collection a bit expensive, but a rather lovely experience! Perhaps I could borrow your rig for a bit - a Mesu 200 and a pair of 106s would be nice...

 

The last time I looked, Gav, the fluorite 106Ns were not fetching £3000. They have the blue rather than the red bands round them.

Olly

Second hand Tak FSQ106N. Mine came in at about £2K. The other one, Tom O'Donoghue's, was a bit dearer but was much younger when he bought it. If (unlikely ) Tak offered to swap my Fluorite 106 for their latest Flatfield 106, I would decline. I prefer the old one. It is less sensitive to focus drift while cooling and I don't want to use the reducer. The captain's wheel hasn't made many friends, either. Give me a 106N (or two!)

I love this rig because it works:

Olly

I've bought lots of kit from abroad and also sent quite a lot. In my experience the best carrier by far is UPS but there may be local effects in play here.

Olly

1 hour ago, mikeDnight said:

It was a Meade 26mm Plossl that got me rethinking my eyepiece collection. It's clarity and sharpness really appealed to me, but for the life in me I could never allow anything with Meade written on it in my eyepiece case. I just don't like the company! I've never noticed mushy views through the TV Plossls though, they are sharp and contrasty to me! You weren't looking through a Meade SCT at the time we're you Olly? 

  I'm heartily inclined to agree with your dislike of the company, for sure, and I haven't tried my Meade Plossl in our 14 inch Meade SCT! (I wasn't expecting this scope to be anything like as good as it is, by the way, but in fairness to an unpleasant company it is actually very good!)

Olly

I wanted to try a TV Plossl so I bought a used 25mm. It's good, but quite honestly the improvement on an equivalent Meade Plossl is, to my eye, marginal. Where the TVs come into their own is in the more exotic designs. I don't have words of praise enough to describe the 13 Ethos but there are other TV greats as well, notably the 19 Panoptic in a more moderately priced EP. Do I think the best way to spend the price of a TV Plossl is on a TV Plossl? Actually no - and I'm a huge TV fan with 6 in my box. But I'm not a great Plossl fan at the best of times. I once heard them described as 'mushy' which is going far too far, but they don't have the crispness I like in an EP. Of course they're notoriously personal things, EPs.

Olly

Edit: Your photos of eyepieces on a star chart are very attractive one in their own right. I might copy that one for our kitchen!

7 hours ago, cuivenion said:

Hi Olly. So if stack a set of subs from one night, get an image and then stack images from a different night and get an image; if I stack the two produced images is that stacking the stacks?

As Carole says, yes, that's right. In truth I often do this myself but I'm using cooled CCDs which produce low background noise. The advantage of calibrating the subs individually and then combining them using a sigma clip routine is that the total number of images used to define what's normal (as opposed to what are rogue outlying values) is higher so the rogues are better identified and normalized. If you have only two stacks to stack the only option is to combine using 'average' which will not be as effective against noise.

Olly

Good! But you'll be knocked out when you see what flats will do for you.

Olly

I think that by 'stacking the stacks' Carole means combining a stack from one night with a stack or stacks from other nights, and you can certainly do this. You'd need to find the best way to weight them in the process. Under no circumstances would I put different sub lengths or settings into one stack. So, assuming consistent skies and the same settings, you'd just weight the stacks based on their total integration time.

The best way to do it, though, is to calibrate each individual sub in the entire shoot without combining them and so generate a new collection of individual subs duly calibrated. You then take these calibrated subs aside and stack them as a separate operation, obviously without any calibration files since that has been done to each sub already. This way you get the maximum value from the Sigma Clip algorithm and the best benefit from dither (even if you weren't dithering between subs.)  I suspect that this method would be of even greater benefit to DSLR imagers since it would attack the background 'colour mottle' problem most effectively.

Now, different sub lengths. Do it only if you know why you are doing it. Of the 100 or so images on my gallery site I've done it precisely twice, once on M42 (which everybody has to image in multiple sub lengths) and once on M31 (where I'm not even sure it did any good at all.) I never worry about white clipping stars. You can pull the colour into the cores in post processing and if you expose so as to avoid clipping stellar cores you won't go deep enough. The key thing is to look at your linear stack. If a galaxy core isn't burned out there then it doesn't have to be burned out in the final image because you already have the data in the stack.

Olly

38 minutes ago, Nigel G said:

Looks like the sensible thing to do is upgrade camera.

I have thought a lot about cameras and what to get.

I love the idea of a mono but would it be a good choice with so few clear nights to gather data, would a OSC be the wise choice.

I'm going to tackle this by reducing the exposure times and will try darks as it will do no harm. in fact I could add some darks to the data I have, I know its not ideal but I would see a difference to banding if it made a difference.

Nige.

My answer is always the same. Mono is fastest. On NB it is way faster and it opens up the moonlit nights for imaging.

Olly