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Suggestions for a large DSO imaging telescope please...


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I have been imaging with a DSLR and webcam through my F5 8" newt for about eight years now. It is about time I started updating my setup since I really want to bet more involved in DSO imaging, with a bit of planetary thrown in.

Currently using an HEQ5 mount, I have my heart set in a Mesu 200. With a bit of an apature craving, I was looking at the 14 inch edge hd. However my comfort zone is the newt, an I have no experience of issues such as mirror flop.

My budget will also allow for a CCD, but Im really not sure if this is the best scope for the job. The setup will be inside an observatory that can take upto 16 inches. I can spend about 6 to 8 k on the scope.

Any pointers greatfully received!

Cheers,

Andrew

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With your budget you have lots of options. A couple things to help narrow down the field: 

1). Why are you wanting large aperture? Are you wanting it for the actual size of aperture or for the long focal lengths that come with it? Remeber for DSO imaging aperture isn't king here like it would be for plantary or visual. So don't choose a scope just because it has a large aperture. Though with that said if you have very good skys where your obsy is aperture can help with resolution but to stress you skies need to be top notch for this to come into play. Most peoples skies are good enough so there are other factors you should consider.

2). What are you wanting to image? Nebula or galaxies? Wide field, mid range or long FL AP? With nebula your driving factor will be the fast f/ratio and for galaxies it's more about FL. Depending on your FL preference you have plenty to choose from.

3). Depending on the answer to the above question a Newt might not be able to give you what you are wanting so your only options will be SCT style scopes where the exit pupil is out the rear instead of the side. Don't be afraid of going down this route. The learning curve is very minimal, especially since you have collimating down.

4.) Make sure to purchase a camera that matches your scope and your skies. You could spend tens of thousands of a camera and scope but if they are matched properly with the sky your images will look just as good as someone who has a kit that is a fraction of what you paid for yours.

5.) Depending on what you are wanting to image there are several very nice high end refractors that fit into your budget. There are fast fracs with shorter FL and slower fracs with long FL. These can produce some splended high quality images. Plus there is a lot less upkeep with fracs versus any type of reflector. I would definately put a refractor on your short list. Maybe even pair it up with a bit smaller reflector to give you options of wide field or long focal length imaging.

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If you want to get into high quality DSO imaging then having more than one focal length would be best. Having only one is like having only one prime lens for your daytime camera. Frustrating! On your budget you could have at least two and that's what I'd want.

Your choice of the Mesu is sound. I have been using one for over two years. Excellent.

Now, this 14 inch business. My friend and co-imager Yves Van den Broek, whose 14 inch ODK I operated in our observatory, has recently sent me a comparison image taken with smaller pixels in a smaller, 10 inch ODK also based at my site. There is no significant difference between these images. The C14 has an almighty focal length, a very slow F ratio and cannot cover a full frame camera once the reducer is fitted - as I think you'd want to use it. Why exactly would you want to use such an instrument? You'd need to be careful to go for a camera with large (or binnable) pixels in order to be sampling at a workable and productive rate.

I'd have a fresh start in terms of thinking about your targets, first off. Then I'd match a good CCD monochrome camera to the scopes you'd shortlisted for those targets. 

Olly

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Here at the University we use 14" Meades for the students with e.g. QSI 3x3 binned mono CCDs, giving about 1" per pixel (we never get FWHM better than 2-3").  The result is a very impressive imaging setup, albeit with a fairly small field of view (30 arcmin or so I think).  But as Olly says, you do have to match those CCD pixels to your FL.

NigelM

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There's no mirror flop in EdgeHD scopes ;)

As per the advice above, decide on the image scale you desire, depending on your skies average transparency and seeing, anywhere between 0.4 and 2.5 arcseconds per pixel will serve you well. This can be achieved using binning as required on smaller pixel cameras.

SCTs are very easy to collimate, stay collimated and easy to manage, with good colour correction, a flat field, and leave you lots of space in the obsy. The available 0.7 reducer is well matched, and the scopes performance are proven.

A decent triplet and an SCT cover most bases, perhaps a short focal length refractor for wide field :)

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There's no mirror flop in EdgeHD scopes ;)

As per the advice above, decide on the image scale you desire, depending on your skies average transparency and seeing, anywhere between 0.4 and 2.5 arcseconds per pixel will serve you well. This can be achieved using binning as required on smaller pixel cameras.

SCTs are very easy to collimate, stay collimated and easy to manage, with good colour correction, a flat field, and leave you lots of space in the obsy. The available 0.7 reducer is well matched, and the scopes performance are proven.

A decent triplet and an SCT cover most bases, perhaps a short focal length refractor for wide field :)

You really reckon 0.4 arcsecs per pixel is worth going for, Tim? I'm not doubting but I'm curious. I've never tried. Boy, it sounds quite tight!!

Olly

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Thankyou all for your invaluable feedback ; much appreciated!

My own experience of imaging is limited to an 8" newt and a dslr, my main focus (sorry forcthe pun) has been on galaxies, clusters and and bright nebula such as M42. Ive also played a bit at imaging jupiter with a webcam, but my setup will never producing anything showing good detail.

Reading all your comments, perhaps a good route to follow is a dual setep of an ED refractor for widefield nebula and a SCT for planetary and smaller targets?

nmoushon: My experience, limited as it is, is that larger apertures give greater detail in the view. My skies are reasonably dark, however living in England, about 4km from the Wash (the north sea), there can be a fair bit of turbulence in the air. I am looking to set up inside a 2.7m pulsar dome which I hope to fully automate at some point. If I use two scopes side by side this may allow for planetary/galaxy and also widefield nebulae. Purhaps a 4" ED refractor and a 12" SCT?

Dave: That 160mm APO certainly looks substantial!

Olly: It was your pro-mesu reviews over the last year or so which has convinced me that this is a good way to go!

Thankyou once again for any input.

kind regards, Andrew

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Thankyou all for your invaluable feedback ; much appreciated!

My own experience of imaging is limited to an 8" newt and a dslr, my main focus (sorry forcthe pun) has been on galaxies, clusters and and bright nebula such as M42. Ive also played a bit at imaging jupiter with a webcam, but my setup will never producing anything showing good detail.

Reading all your comments, perhaps a good route to follow is a dual setep of an ED refractor for widefield nebula and a SCT for planetary and smaller targets?

nmoushon: My experience, limited as it is, is that larger apertures give greater detail in the view. My skies are reasonably dark, however living in England, about 4km from the Wash (the north sea), there can be a fair bit of turbulence in the air. I am looking to set up inside a 2.7m pulsar dome which I hope to fully automate at some point. If I use two scopes side by side this may allow for planetary/galaxy and also widefield nebulae. Purhaps a 4" ED refractor and a 12" SCT?

Dave: That 160mm APO certainly looks substantial!

Olly: It was your pro-mesu reviews over the last year or so which has convinced me that this is a good way to go!

Thankyou once again for any input.

kind regards, Andrew

Andrew, You are correct and saying larger aperture gives better views (visually) but when it comes to imaging the more aperture doesn't mean you will get more data. The f/ratio is what determines how much data you collect. A 12" SCT @F/10 will collect a LOT LESS data than a 12" F/4 Newt. Your image scale is what will be different here as the focal lengths are different. Now for planetary aperture does play a bigger role in contrast and detail but I'm not a planetary person so I best leave the detailed explanation to someone with more experience. But in regards to DSOs aperture plays a very minimal part, so minimal that you only need to consider it just for the sheer size of the telescope.

Setting up a dual rig I think will be your best bet. A good refractor for wide field and then I would suggest the 11" EdgeHD. The 11"SCT will do great for plantary and galaxy hunting. You can even put the reducer on it and it will be pretty decent to image so detailed shots of larger nebula. Then the fast refractor will give you your wide field shots that can get all the really faint nebula.

One thing about the Mesu is I'm pretty sure I've read on here that its not the best mount for remote/automated setups. So you might be out of luck (or maybe very limited) as to exactly how remote/automated you can make your setup. I'm sure Olly can pipe in on this and explain or correct me.

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A 12" SCT @F/10 will collect a LOT LESS data than a 12" F/4 Newt.

Not on a single object - it will collect the same amount of light (providing it fits in the field of view of the SCT of course!). So if you are happy with the smaller field of view then an SCT can be much easier to handle than a big Newt.

NigelM

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Not on a single object - it will collect the same amount of light (providing it fits in the field of view of the SCT of course!). So if you are happy with the smaller field of view then an SCT can be much easier to handle than a big Newt.

NigelM

I should add: "A 12" SCT @F/10 will collect a LOT LESS data than a 12" F/4 Newt with the same exposure length." Now this does play differently when imaging galaxies instead of nebula. Nebula this holds true but with galaxies it does not. Sorry if I didn't get that across.

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Thanks for all your good advice so far.

So, as a starter for ten, what about a set-up comprising of a Skywatcher Espirit 100ED triplet & flattener : http://www.firstlightoptics.com/esprit-professional-refractors/skywatcher-esprit-ed-100-pro-triplet.html to allow for imaging of wide field nebula together with a CCD such as the QSI 683: http://telescopes.net/store/qsi-683wsg-8-8-3mp-cooled-ccd-camera-w-8-pos-filter-wheel-and-integrated-guider-port.html

Not too sure it would fit in the domed observatory, but for my aperture fix, a 300mm newt for galaxy and planetary imaging together with a suitable CCD...whatever that may be! : http://www.firstlightoptics.com/reflectors/skywatcher-explorer-300p-ds-ota.html

What do you all thing? Would any of this set-up set alarm bells ringing over anything?

Many, many thanks once again.

Andrew

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Thanks for all your good advice so far.

So, as a starter for ten, what about a set-up comprising of a Skywatcher Espirit 100ED triplet & flattener : http://www.firstlightoptics.com/esprit-professional-refractors/skywatcher-esprit-ed-100-pro-triplet.html to allow for imaging of wide field nebula together with a CCD such as the QSI 683: http://telescopes.net/store/qsi-683wsg-8-8-3mp-cooled-ccd-camera-w-8-pos-filter-wheel-and-integrated-guider-port.html

Not too sure it would fit in the domed observatory, but for my aperture fix, a 300mm newt for galaxy and planetary imaging together with a suitable CCD...whatever that may be! : http://www.firstlightoptics.com/reflectors/skywatcher-explorer-300p-ds-ota.html

What do you all thing? Would any of this set-up set alarm bells ringing over anything?

Many, many thanks once again.

Andrew

The triplet is a pretty good choice along with the CCD. Though you might want to start a new topic to make sure you match a good CCD to you scope choices.

But that Newt is not the best to do planetary and long focal length imaging. It will be a good step into long focal length imaging with 1500mm of FL so thats the good side. Because guiding at really long focal lengths is very demanding. You will also want to budget for a good guide cam and OAG. You will have plenty of small objects to image with this but to get the really small stuff you will want to be near or over 2000mm FL. This goes for plantary imaging as well. The reason the Newt isn't the best is because you will get way more FL per inch of aperture in a SCT than a Newt. I guess you need to decide what kind of object your are wanting to image. If you are like me and want all the fine detail in galaxies, get all the super small galaxies and get detailed PNs then the Newt is not going to work and you will want to look at a SCT. But if you are wanting a mid-range FL scope to image some of the larger galaxies and still get to image some of the good up close detail shots of nebula then the Newt will fit your bag just fine. It a good bit faster which will help cut your imaging time down a bit.  But really consider what kind of targets you are wanting to image with a "longer" focal length setup. You have the fast wide field covered with the triplet so this is the final bit.

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You already have an 8" newt which gives a medium field of view. you have an opportunity at getting some wider field like an ED 80 and then something with a long focal length, the SCT have been mentioned, I'd throw in the new  GSO Ritchey Chretien carbon fibre truss scopes (10"-16") as another alternative they look the goods and would be great for long focal length work etc.

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Thanks nmoushon, you have been a great help. You have given me plenty to think about. I'll come make again in a few weeks after a bit more research.

Rustigsmed, I do like the look of the 16" RC, however, (I think), unless these have been corrected, they would not be much good for imaging apart from optical light only. That said, I'm sure that would still work fine for planets and most small galaxies?

The deep field, corrected versions of the RC are a bit too expensive sadly...Also, not too many reviews about for Altair Astro RC truss.

Kind regards,

Andrew

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