alan potts

27 minutes ago, wxsatuser said:

If it's the 7704

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=2ahUKEwi_5pr8-KLmAhUzpnEKHSaiBV8QFjAAegQIBBAC&url=https%3A%2F%2Fwww.sciencecenter.net%2Fhutech%2Fborg%2Ftechdocs%2F7704.pdf&usg=AOvVaw3PbYOobIbtLIfX0xvZfm99

This appears to be the item attached to the scope, I will have a read, I have these spacers too. It would appear I need to insert this thick rear spacer.

Alan

5 hours ago, michael8554 said:

Is there a Triplet Reducer on the scope that you haven't mentioned? 

That has a 130mm backfocus. 

Just my guess........ 

Michael 

There is a reducer on the rear of the scope but it just came with two fittings and a couple of thin spacers, one fitting is for Canon cameras and the the other for CCD's. If the backfocus is as large as 130mm then I am surprised I have something reasonable at what would be around 38.5mm. I may well try the Canon fitting and see what happens.

Alan

Nothing new in that statement, all I ever seem to do is ask for help.

I have tried out my Borg 77ED ll now I thought the backfocus for this was 55mm, but with the zwo 071 fitted with both 16.5 amd 21mm sleeves I cannot get focus, I can get close but nowhere near sharp.

So I removed the 16.5mm sleeve and got focus, maybe not exact but I was working in the dark with rather cold hands. I attach a picture of M45. Now while it seems reasonable in the centre it has tell tale signs of wrong spacing in the corners with elongated stars.  This is no flats or anything, just 4x 2mins at F4.3, does anyone know anything about this scope as I can't see much on the Net apart from pictures which when you have one are of little use.

A little more information, the scope does have a reducer fitted to the rear of the scope bringing it down to a F/L of 330mm and F4.3, I have two fittings with the scope, one for Canon cameras and one that my Zwo's will fit to, both screw directly to the rear element.

Alan

2 hours ago, vlaiv said:

Well, you have quite a selection to choose from.

I would personally go for M/N, but 115mm APO is also an option for wide field.

You would need 9 panels to cover M31 for example.

It would seem that taking 9 panels will take up too much time compare to single panel, but in fact you will get almost same SNR in the same time as using smaller scope that would cover whole FOV in single go (provided that you also have F/5.25 scope). I'll explain why in a minute.

First thing to understand is sampling rate. I've seen that you expressed concerns about going at 2.29"/px. Fact is - when you are after a wide field that is really only sensible option - to go low sampling rate (unless you have very specific optics - fast and sharp, only in that case you can go high resolution wide field). Take for example scope that you were looking at - 73mm aperture. It will have size of airy disk of 3.52 arc seconds - aperture alone is not enough to resolve fine detail - add atmosphere and guiding and you can't really sample at below 2"/px. I mean, you can, but there will be no point.

Another way to look at it is that you want something like at least 3-4 degrees of FOV. That is 4*60*60 = 14400 arc seconds of FOV in width. Most cameras don't have that much pixels in width. ASI071 is 4944 x 3284 camera, meaning you have only about 5000 pixels in width. Divide the two and you will get resolution that it can achieve on wide field that covers 4 degrees - 14400/5000 = 2.88"/px. So even that camera can't sample on less if you are after wide field (not to mention the fact that OSC cameras in reality sample at twice lower rate than mono).

Don't be afraid of blocky stars - that sort of thing does not happen, and with proper processing you will just have a nice image even if you sample on very low resolution.

Now a bit about the speed of taking panels vs single FOV. Take for example above M31 and 9 panels example.

In order to shoot 9 panels you will need to spend 1/9 of time on each panel. That means x9 less subs for each panel than you would be able to do when doing single FOV with small scope. This also means that SNR per panel will be x3 less than single FOV if you use the same scope, but you will not be using same scope. Imagine that you are using small scope that is capable of covering same FOV in single scope - it needs to have 3 times smaller focal length to do that. So it will be 333mm FL scope. Now we said that we need to match F/ratio of two scopes, so you are looking at F/5.25 333mm scope. What sort of aperture will it have? It will be 333/5.25 = ~63.5mm scope.

Let's compare light gathering surface of two scopes - first is 190mm and second is 63.5mm, and their respective surfaces 190^2 : 63.5^2 = ~9. So large scope gathers 9 times more light, which means that it will have x3 better SNR - that cancels with time needed to spend on each panel - you get roughly the same SNR per panel as you will for whole FOV.

You end up with same result with larger scope and doing mosaic in one night as you would with small scope of the same F/ratio that covers same FOV in one night.

There are some challenges when doing mosaic imaging - you need to point your scope at particular place and account for small overlap to be able to stitch your mosaic in the end (capture software like SGP offers mosaic assistant and EQMOD also has small utility program to help you make mosaics). You need to be able to stitch your mosaic properly - APP can do that automatically I believe, not sure about PI, but there are other options out there as well to do it (even free - there is plugin for ImageJ). You might have more issues with gradients if shooting in strong LP because their orientation might not match between panels - but that can be dealt with as well.

Unless you really want small scope, you don't need it to get wide FOV shots - you already have equipment for that, just need to adopt certain workflow to do it.

Well thank you for taking the time to type all this, it is something to bookmark and come back to, I need better software than I have at the moment, I am thinking of getting APP as I don't have anything effective for gradients, something I seem to get more of now with the 071 as opposed to the Canon. I also have another camera to mess with a 183mc, not so sure why I bought this now, maybe not my best ever move.

I imagine if I use the Borg which with the 071 will have a massive FOV, of about 4 degrees and I guess this is decent quality in the optics department. I even tried earlier to put the Borg on the mount but despite 2 million bits and pieces could not find screws the correct size to fit the guide scope, why does nothing ever seem to fit together without spending another small fortune on more bits.

Alan

I tried about 3 hours last night in damp and frosty weather but nicely clear. I imaged the Soul and part of the Heart (how big is this target).  Not processed yet but the images were poor for other reasons, stretched stars going into the corners.

The spacing for this is quoted at 55mm which according to Zwo you get exactly by putting the spacers together, this works very well with the Hutech flattener which is about perfect as I see it. Maybe this rather larger TS reducer at 360e is not all it's cracked up to be, pleased I didn't pay that for it, it may only be a minor spacing issue but one I don't really understand and best forgotten in my view.

I would soon buy another scope and use the Hutech, which is a very nice piece of equipment that was recommended to me by Steve, one of the Mod team, a man that knows a few things about imaging. 

Alan

6 hours ago, david_taurus83 said:

I had to get a filter drawer Alan for my reducer, same as yours. M48 version, 15mm thick.

https://www.365astronomy.com/ts-optics-filter-quick-changer-for-2-filters-m48x0.75-thread-length-15mm-including-filter-drawer.html

David, this would be fine if this business ever replied to an e-mail, I asked 2 questions of them a long time back and got nothing. However the ZWO spacer where this would fit is 16.5mm and that would still leave 1.5mm to fill, shim maybe?

Alan

11 hours ago, vlaiv said:

@alan potts

What scopes do you have already to image with?

Wider FOV is easily achieved by doing mosaics, so you don't really need to spend money on a new scope if you have one that you are pleased with, but gives narrower field of view than you would like.

It is just a matter of proper acquisition and processing of such data, and although people think that doing mosaics is slower process than going with wider field scope - it is not necessarily so. If you already have fast scope (fast as having fast F/ratio), then doing mosaics is going to be marginally "slower" than using same F/ratio scope capable of wider field with the same sensor (difference being only overlap needed to properly align and stitch mosaic image).

I have a few scopes Borg 77ED ll F4.3,   a 70mm Ed F6 which has a problem of alignment,  a 115mm APO F7 with reducer .79    and 190mm M/N F5.26.     I guess I could also play with the 180mm Mak and the 12 inch Sc, I have mounting gear for them.

Alan

I don't have this catalogue so can't see where it is, it looks fine to me though when all the members do this NB lark, i never know what colour things are meant to be, to me it don't matter, the stars are rouns and it looks like a difficult subject to start with. I thing you've done a grand job on it.

Alan

Lovely image, this Heart takes a wide field. I am going to have a go at its neighbour later on, not sure what I will get as I've had to take out the IR/UV filter to get the .79 reducer into play. Hope I get a result half as good as this.

Alan

Not perfect, go stand in the corner. Looks wonderful to me. You always seem to come up with things that don't get captured so often, or I just don't recognise it.

Alan

Makes one want a 106mm Tak, doesn't it, great image and really jumps out the screen on my setup in the basement.

Alan

Yes looks like the Pacman to me too, a very nice image i have to say, love the colours.

Alan

What can I expect if I use my .79 reducer without a IR/UV filter in place, I cannot see  a way of using one in the Zwo tube set-up and the reducer is way too big on the scope side (67mm) to get a filter on.

Anyone any ideas how I can keep 55mm backfocus and get a filter in the line, I can get a 1.25 inch filter in but that is way too small for 071 sensor. Surely I cannot be to the only to have this issue.

Alan

1 hour ago, ollypenrice said:

 

The Tak 106/Kodak 11 Meg gives 3.5 arcsecs per pixel and, as Dave says, has more APODs than you can shake a stick at. You are welcome to zoom in on mine as much as you like. Fine resolution is lost but there are no screaming artifacts like square stars. This is a tiny crop of the Flaming star from a widefield image so you can see it at full size. This is 3.5"PP so I really don't see what you need to worry about at 2.29.

The full image is here.  https://www.astrobin.com/394025/?nc=user

Olly

 

 

 

 

Thank you Olly, that is a very nice image a always.

I would concur with your statement, Too many cables, i was looking at a complete case full earlier and have to admit I can't even remember what most are for, only remembered 5 (now) ST4 cables one that works on the AZ EQ 6 and all work on the CEM 60. The cable st4 Moderator Rob sent me has very slightly larger plastic connectors, all things are not created equal, it's only about .15mm but it matters. Maybe the 73mm WO is a decent enough scope for wide field and I should get one whilst i still can.

alan

Really nice image, as good as I have seen, you haven't over saturated it which so many seem to do, me included.

Alan

Two years, see you still know what your doing, feels like 2 years since I have had a decent night, now it's snowing. Never realised the crescent was so big, lovely image!!

Alan

I've been wrestling with this one and can't decide which to the extent I thought I may get both. I have a bit of an LED sky glow from the SE where a small town sits. The other nigh the lights went out here and around and it appears a bit worse than I thought though it was reflecting off patchy low cloud. I rather fancied the Optolong based on your two pictures.

Alan

1 hour ago, Laurin Dave said:

If you want wide field I'd just try the Borg with the ASI071 and see what you get Alan before spending money,  it'll have essentially the same FOV and "pp (slightly lower in fact) as a Tak106 and kaf11000 camera combination..  

And yes I too have a collection of Skywatcher finders, diagonals and eyepieces

Dave

My word I had no idea the KAF had pixels that large, twice the size of the 071 almost, like the TAK 106 one of the best scopes on the market. I guess doing what you suggest does cost nothing, snowing at the moment which is a bit of a downer.

Alan

2 hours ago, Laurin Dave said:

Hi Alan..  I believe you’ll need a flattener with that scope, but I shouldn’t worry about that pixel scale being too much, there’s plenty of APODs out there at 3”/pp..  ie Tak106/kaf11000 images, just don’t zoom in too much..  if you want 500-550 mm then you won’t go wrong with an Esprit100, plenty of excellent Esprit100/ASI071 images around..  if you wanted to go shorter still maybe the GT71 at 350mm or so would work well with your ASI183.  Also be aware that WO have 70 and 90mm versions of the RedCat in the pipeline..

so just the usual downsides..   like me, you’ll always want something else as well! 

Dave

Yes the Esprit 100mm, sadly though I don't have that amount of spare cash in my UK, though I could transfer it running the risk of getting stabbed by the wife for spending again. The Esprit is a great scope though. Shorter I already have a Borg 77ll mk2 which I think it 330mm so the 183mc was really only for that. The 071 on the Borg really send the numbers high but maybe I should try it, silly thing is the Borg has been sitting here for over 2 months and so far has not seen a mount.

The only thing that is making me want to move on this now is really only what will be the case after GB leaves the EU, if indeed it ever happens, I like FLO as an outlet and trust them 100%, using them after this could induce customs duties and VAT issues. I guess though Dave on a one off purchase for peace of mind taking a hit is no bad thing.

The only other thing I have against the whole Esprit range is I will be paying for a finder and a diagonal, I have 3 TV 2inch diagonals and WO and 5 different finders, I don't need more. In the event of buying I would ask FLO to remove them and give them as prizes at some event.

Alan

I am strongly considering a new WO 73mm which has a F/L of 430mm. Now this is no issue with my 183MC but on my 071 does give a Pix/sec figure of 2.29 which is a bit more than recommended, something around 500-520mm F/L would be ideal but I see nothing.

If I go ahead with the purchase what are the down sides of this?

Alan 

I like Richard have the 071 and not long since bought. One never knows when new gear will come along. As much as I feel the new 2600 model will be better, I personally am always reluctant to buy anything right at the beginning of a production run, there always seems to be some issues, no matter what, even cars. I rather fancy the full frame model though not so keen on the price tag. I have seen some very nice shots taken with the ASI 294 though, and 1000 is a fairly large amount in any language.

Alan

56 minutes ago, steppenwolf said:

3 hours ago, alan potts said:

A great image Steve, I was so disappointed with this target as I can't get it all in frame. I may do better with the .79 reducer in line but I cannot get a IR/UV filter into the mix without spending what I think is a silly amount (166e + P&P) for a single filter draw and 0.3mm shim.

Thanks Alan. This was one aspect of the longer focal length of the Esprit 150ED that concerned me when I first got it but now I like to 'zoom' in on specific features of larger nebulae when imaging with this instrument. A case in point is my current project which is concentrates on just a small region of the Soul Nebula, the Ha of which I captured last night:-

Edited 49 minutes ago by steppenwolf (see edit history)
Only staff can see this message

This was another one that the wheels came off, as it happened it would just fit the frame and for sure would if the reducer was in play, but I got the orientation 90 degrees out and had a lovely 2 hours of the middle bit, apart from the ends missing it was a half decent image, not in your league though.

Alan

A great image Steve, I was so disappointed with this target as I can't get it all in frame. I may do better with the .79 reducer in line but I cannot get a IR/UV filter into the mix without spending what I think is a silly amount (166e + P&P) for a single filter draw and 0.3mm shim.

Its sort of nice to see what can be done focusing on one aspect of the bigger picture, i may well try that, when this weather changes for the better.

Alan

5 hours ago, fwm891 said:

Pixel scale 2.39 sec/p

That will be higher on my 071. I keep wanting to order a 73mm WO from FLO but it gives me 2.27 I think it was, I thought this was a no no, but seeing your photo, i don't see any problems with a larger sec/p scale, think it's a goer before Christmas.

Alan

Thats very nice Francis, something I had a go at but was not able to collect the same degree of data you have there as my scope is F7, sort of interested in one of these RASA scopes as we have the same mounts,

Alan