confusion re Celestron nexstar 4SE

[nora nooby]

AS mentioned I am a complete beginner but have been reading loads. I emailed a couple of shops who deal in telescopes giving them my budget (£400 or so) and what I wanted telescope for (mainly to take photos of nebula)

One came back to me with a suggestion of celestron nexstar4SE which would fulfil all my criteria and suggested i call them which i did. I looked at the details and saw this came with a computerised alt mount. I have read many times that for decent photos an equatorial mount was needed so I called them. I was told that with the mount it has I would be able to take a 2 min exposure no problem. I am now confused. Have I not taken the 'computerised' bit into the equation ? would it be capable of taking a 2 min shot without getting trailing?

[Ags]

Hi Nora, I have used the 4SE mount for some basic AP experiments - look into my threads for some examples of my feeble efforts. Firstly, you can tilt the whole mount with its built-in wedge, giving you an equatorial mount.

So far, so good... The real problem is there is a lot of play in the 4SE gears so the tracking is poor. Using a 400mm focal length telescope, I could manage barely 30 seconds without some sort of wandering causing sizeable trails. I suspect the performance will vary from mount to mount - mine could be a good one or a bad one. I also notice the mount has a tendency to skip gear teeth now and then, causing 'double vision' in otherwise perfectly tracked subs.

Another problem with the mount is that the camera (especially a bulky DSLR) will collide with the mount if you try to image anything north of Perseus. If you stick to alt-az imaging (and you may as well if you can only get 30 second subs) the camera will collide with the mount in the course of tracking.

The mount is also only strong enough for lightweight scopes, like a small mak or a short-tube refractor, neither of which are very good for imaging. My next experiment will be to try using the mount as a crude platform for a widefield camera lens - the tracking is probably adequate for a 30 - 50 mm lens.

[Ags]

By the way, the 4SE is a maksutov telescope, which is completely unsuitable for imaging nebulae. Its photographic speed is F13 which is 6 times slower than the F5 ST80 I put on the 4SE mount for actual imaging. So the 30 second exposures I was referring to would take about 180 seconds with the Mak, with six times as much star trailing /wandering. In fact it would be worse - the focal length of mak is three times longer than the ST80 so the trails would grow three times faster for six times as long.

I would say forget deep sky photography with the maksutov. Nobody uses it for that and I feel you were poorly advised. As a visual instrument it is very nice for observing the planets and the moon. But you could spend the same money and get a 127mm mak from skywatcher which would probably be a better visual instrument (but would be even worse at photographing nebulae).

[E621Keith]

Hi Nora,

I'm afraid there are no astrophotography set up within your budget that is capable of getting decent image of nebula. Nebulae is very dim, so imaging them require long exposures and accurate tracking. A HEQ5 mount is the minimum requirement and that alone cost around £750. The basic scope a ED80 cost around £400. On top of that you will need a guiding system which will cost an additional £300.

There is no way you can get 2 minute subs with a 4SE without trailing. Apart from the focal length of the Mak, there is no way of doing accurate polar alignment with the 4SE.

I suggest you stick to visual for now. May be you can try planetary imaging which is less demanding on the mount.

[Ant]

I think you can get started for your budget...

But you need to be aware of the limitations - you also do not mention the camera that you have?

So something to think about.

First Light Optics - Skywatcher Startravel 80 OTA - £90 OR

First Light Optics - Skywatcher Startravel 102T OTA - £163

First Light Optics - Skywatcher EQ5 Deluxe - £229

First Light Optics - Single-Axis D.C. Motor Drive for EQ5 - £75

ST80 + EQ5 + RA Drives = £394

ST102 + EQ5 + RA Drives = £467

So not ideal - but it would get you started.

Once you ready to spend a little more money, you can either sell the above and buy something like an HEQ5 or you can stick with the mount that you have and buy the First Light Optics - SynScan PRO GOTO Version 3 Upgrade Kit for EQ5 kit which is £290. But gives full laptop control with guiding commands etc...

You can get started for £400 - but it is the first step on the ladder. I hate to stress the point but feel it's vital that you go into this with your eye's wide open.

Besides this is the way that most of us started. It's a great way to learn how things work the get processes sorted, problems solve things one at a time (while things are still fairly simple) and then add to what you already know, by adding stuff (guide cam's/laptop/filters etc) one at a time.

Hope that helps.

Ant

[Ags]

+1 ant!

Some great pics ( far better than mine ) have been posted using the ST80, and the EQ5 is a great mount that will serve you well. The ST80 is very forgiving because of its fast photofraphical speed and short focal length.

The ST80 can even be pressed into service later as a guidescope when you extend your imaging to include guiding. But be aware that the ST80 is a little limited as a visual instrument.

[nora nooby]

thanks all for the helpful replies. I will scratch the nexstar off my list. I will into the other ones mentioned. I am all to aware that my budget is miniscule for what I would like! But I either have to save up for some months maybe a year even or go with a second choice set up and I am so eager to get going. But also dont want to waste money !