Upgrades for Nexstar

[Nessy]

Hi, I have a few queries with regard to imaging on the new Nexstar 8....

For short-exposure I will need a T-Mount and adapter? If I get a radial guider which would be used for long exposure later would I not need to get one of the above?

If I get a tele-extender, what else do I need?

I would like to get a wedge at some point - what is recommended for the NexStar 8?

Is it best to get individual Filters and just image, change, image etc or is it worth getting filters on a wheel/slide? If so, any recomendations?

Wow - so many questions! Essentially I would like to start off doing short and then move to long but buy stuff that will allow both thus saving money!

Any help much appreciated.

[Nessy]

Or perhaps a Flip-Mirror system? Anyone used one of these/rate one?

Thanks all....

[GordonCopestake]

Hi Nesy. I am not an imager but I dabble a little. Until someone more experienced comes along (CC? MartinB? Rog?) I'll try and answer your questions. Bear in mind I could be completly wrong though!

1) if you are using a dSLR and prime focus photography (the norm) then you will always need a T-Mount and adapter. If you are using a dedicated astro camera they tend to come with nosepieces (I believe). I'm not sure about the radial guider as most people use dedicated guide scopes (although i've recently learnt that KCCD tools can use a single camera for both imaging AND guiding

2) By a tele-extender do you mean a barlow? If it is a barlow lens you mean then the camera (or eyepiece) simply goes into the barlow first and then the barlow goes into your focuser. There is no other equipment needed.

3) As for wedges, Celestron make one but it's not the highest quality. APT, Milburn, Ambermile all make decent wedges but be aware they are expensive

3) The filter wheels/slides are used in LRGB imaging I believe, and unless you intend to image in seperate colours then you dont need a wheel. Of course if you want to then feel free to get one, but in my mind it's more cost that is not needed if you are just starting out.

4) Vixen make good flip mirrors, but to me they are something of a waste as you need to refocus once you have centered your target. Personally I would use a secondary 'scope / finder to locate your target rather than use a flip mirror.

My advice would be to start with what you have and then see what you need once you have experience. Dont go spending a load of money on stuff until you know that you can't do what you want with what you already have.

[MartinB]

Nessy, the first thing you need to buy is a focal reducer since the 2000mm focal length of the NS8 is an advanced imaging challenge needing very precise guiding, alignment and focussing. The problem with using a DSLR is that because of the big chip you can't reduce far before you get vignetting. A Celestron 6.3 reducer should be ok though and it will be handy for visual stuff too.

I agree with Gordon - you really want to keep it simple initially. Moon, Saturn and Jupiter in Alt Az with a Toucam are good for starters. The Toucam will do a better job on Saturn than your DSLR. Moving onto DSOs try imaging in Alt Az on some brighter targets - brighter globular clusters such and M13 and M3 along with open clusters such as M44.

Even with a 6.3 reducer the focal length is still quite long so for dimmer results you will need to go longer than the 40 secs you will be able to manage in alt az. With a wedge I have managed 2 mins unguided with an AP 6.7 reducer although a bit hit and miss. If you are committed to the DSLR route I think you will need to look at getting a wedge. The HD Celestron wedge is like a car without a gear box unless you buy the upgrade kit for "accurately" adjusting alt and az. The wedge is ok the az adjuster is poor. Celestron should hang their heads in shame for the amount they charge for the upgrade. It is useable though and I have had some reasonalbe results. Best to buy second hand. Alternatively keep your eyes peeled on ukastrobuynsell for a quality wedge but even second hand they aren't cheap. I paid £350 for my APT wedge second hand - never regretted it though.

One great thing about a wedge is that they are robust pieces of kit which you can cover up and leave set up in the garden polar aligned.

If you aren't committed to DSLR you can look at modded web cams - this would allow you to use a 3.3 reducer or even the wonderful fastar system.

As for guiding I would advise against a radial guider if you want something that you will use long term. They do have the advantage of using the same light path as the camera so no problems with flexure or mirror flop but the FOV is small so finding a good guide star is going to be a real headache. A better bet is to fit some rails courtesy of Rother Valley Optics and get a cheap refractor to piggy back on the NS8.

However, auto guiding is a complex business and manual guiding is guaranteed to give you serious neck ache and make you loose the will to live. Best to go as far as you can unguided initially. After you imaging induction you will be getting a much clearer idea as to how you want to progress.

[Nessy]

Thanks Martin - appreciate the advice and I think I will take note and go with the basics first.

The tele-extender was something I read where you can put the eyepiece in with the T-Adapter so you can achieve the zoom of the eye-piece. Have I misunderstood - does the standard T-Mount and Adapter allow this?

Thanks again,

Chris

ps To all those who told me the mount was THE most important thing with imaging and that the 10" LX75 was NOT suited to the mount (I was thinking of getting one of these).....wow I really can see how right you were!