A prospective replacement for Orion XT8

[Ishan Mair]

Hi.

I've been thinking of selling my XT8 as its cumbersome to transport. Its been with me for 5 years now. Havent used it to its full potential, largely due to that. Its given me good views of a few Messier galaxies,  clusters and nebula. But to be honest, never the structure in any of those galaxies (not even Andromeda) from a fairly dark sky. I'm not complaining, as that could be due to my near-zero abilities to collimate and the bumpy ride it takes every time to reach a dark sky site. So I am now looking for a portable yet capable replacement. The length of the tube makes it inconvenient to take it up-down the  stairs. Plus, it barely fits in my hatch-back.

I'm interested in deep-sky observing especially galaxies. It would be great if you would suggest a scope.

Clear skies.

[Peter Drew]

Hello Ishan.  I have a XT8 and for galaxy and other Deep Sky Object viewing I'm finding it hard to think of a replacement that would be an improvement that wouldn't be even larger overall. Aperture is everything for this type of observation and a larger aperture, even if a shorter tube version would still present you with similar management difficulties. It's worth mentioning that you need a very large telescope to see much detail in galaxies visually, images that you may be familiar with will have been generated photographically. 

[jetstream]

Hi Ishan, a question might be how dark are the skies you are observing from? The dust lanes of Andromeda show even in mildly LP skies and M27,M57 etc show very well too.

Aperture will help regardless of LP, but the larger ones really love dark skies( as all scopes do). A suitcase truss dob or a travel dob might fit the bill for you in the 12"-16" range, or bigger. They get pretty expensive I think however.

Collimation is very easy with the right tools- a 5 minute job from scratch and about a minute to adjust the primary.

[Scooot]

http://www.orionoptics.co.uk/VX/vx10-10l.html

You'd use the f4.8 on one of their dob mount's a lot. Very easy to carry around, transport and store. A little more aperture and it holds its collimation very well.

[Peter Drew]

Do they ship to India? 

[Ishan Mair]

Thanks everyone for taking time to read and replying.

http://www.orionoptics.co.uk/VX/vx10-10l.html

You'd use the f4.8 on one of their dob mount's a lot. Very easy to carry around, transport and store. A little more aperture and it holds its collimation very well.

I checked out its specs. Its only a couple of inches shorter than XT8. Might pose the same problem. Extra aperture makes me think about it though...

Hi Ishan, a question might be how dark are the skies you are observing from? The dust lanes of Andromeda show even in mildly LP skies and M27,M57 etc show very well too.

Aperture will help regardless of LP, but the larger ones really love dark skies( as all scopes do). A suitcase truss dob or a travel dob might fit the bill for you in the 12"-16" range, or bigger. They get pretty expensive I think however.

Collimation is very easy with the right tools- a 5 minute job from scratch and about a minute to adjust the primary.

I've always been confused as far as rating my sky is concerned. Last outing, I could very easily see the Milky way in Auriga and little beyond that towards Sirius. Cygnus was setting and the MW was distinct and clear in that region as well. Andromeda was just visible to naked eye with direct vision though M33 was not even with averted vision. M33 was a little difficult through the scope as well. Double cluster in Perseus, Beehive cluster in Cancer were easy to spot with naked eye. A 30 degree light dome towards north and small light domes were visible in few directions. That night I could just make out the innermost dark lane in Andromeda in direction of M110 through the scope. 

I do not collimate at the dark sky site. I use just a collimation cap with a hole at centre. Is star test necessary under the dark? I've never seen those ring patterns of a defocused star. It looks like a light filled donut. I may not be allowing the scope to cool down. I find it too daunting to do any kind of collimation in the dark. In the dark, how can I check whether the complete reflection of primary mirror ( 3 clips) is visible in the secondary?  You do it in 5 min from scratch. Wow! What tools do you use and recommend?

If you want to see more detail in galaxies than an XT8 can provide you are going to have to go up in apertue.   If you are going to do that within a reasonable budget than it is going to be a dob of some kind and you are going to have to learn to colimate it.

Even if you go to a STC or a Mak so that the scope is shorter and lighter you are going to need at least 8" of aperture to get what the XT8 showed you.

So, a Celestron NexStar 8SE is going to be smaller and lighter than the Xt8, and it is a got to scope.   

http://www.firstlightoptics.com/se-series/celestron-nexstar-8se.html

Add a .63 focal reducer and wide field eyepiecs for your large DSOs.

Perhaps something like a Truss Tube Dob - the 250 PX for example.

More aperture and it comes apart

http://www.firstlightoptics.com/dobsonians/skywatcher-skyliner-250px-flextube-dobsonian.html

How about an 18" that breaks down into pieces you can transport?  This will pull in 5X the light of the XT8

http://www.firstlightoptics.com/dobsonians/sky-watcher-stargate-450p-truss-tube-dobsonian.html

Mak or SCT will be compact. That seems good. But does its large f ratio adversely affect visuals of deep sky?

Hello Ishan.  I have a XT8 and for galaxy and other Deep Sky Object viewing I'm finding it hard to think of a replacement that would be an improvement that wouldn't be even larger overall. Aperture is everything for this type of observation and a larger aperture, even if a shorter tube version would still present you with similar management difficulties. It's worth mentioning that you need a very large telescope to see much detail in galaxies visually, images that you may be familiar with will have been generated photographically. 

I use my other setup for astrophotography. The images are indeed not comparable to what we see. But I enjoy both - imaging and visual. Besides, other people report seeing structure in some bright galaxies. So that's what I am really after.

[jetstream]

You have good skies Ishan, and nothing brings DSO like dark skies.

I use a separate sight tube and cheshire, but a combination sight tube and cheshire will work just as well. The set I use is Catseye system from the USA, highly recommended, but expensive.

The system includes a clip on LED and I also use my headlamp to illuminate things in the scope at times.

Just loosen the sec stalk, make the sec look round and centered under the focuser using sight tube.Tighten stalk.

Then adjust the sec screws to line the sight tube crosshairs up on the primary spot.

Then insert the cheshire and use the primary screws to center the dot in the "hole". Done.And very good.

I did my truss dob for the first time the other day and it took about 5 mins and this method is very accurate. If I were you I would use a sight tube/cheshire combo as the Catseye stuff might be hard to get there.

How does M82 look in your scope at a dark site using a 12mm or so eyepiece- can you see the central structure?

[Ishan Mair]

Even though the Mak and SCT will be physically  shorter but will have longer focal length than a Dob with comparable aperture.  That means the field of view will be narrower which makes them less effective for large DSO like the Andromeda Galaxy, M31.   However you can use a focal reducer to effectively reduce the focal length to get wider views.  Or you can use  wide view eyepieces or a combination to get much wider views.

I have not used any kind of filters ever, so many nebula like Veil are unknown to me. With all the inexperience I ask you : How many DSOs within reach of an 8" scope are larger than 1 degree? How well do small aperture (4 - 6") scopes work with filters?

You have good skies Ishan, and nothing brings DSO like dark skies.

I use a separate sight tube and cheshire, but a combination sight tube and cheshire will work just as well. The set I use is Catseye system from the USA, highly recommended, but expensive.

The system includes a clip on LED and I also use my headlamp to illuminate things in the scope at times.

Just loosen the sec stalk, make the sec look round and centered under the focuser using sight tube.Tighten stalk.

Then adjust the sec screws to line the sight tube crosshairs up on the primary spot.

Then insert the cheshire and use the primary screws to center the dot in the "hole". Done.And very good.

I did my truss dob for the first time the other day and it took about 5 mins and this method is very accurate. If I were you I would use a sight tube/cheshire combo as the Catseye stuff might be hard to get there.

How does M82 look in your scope at a dark site using a 12mm or so eyepiece- can you see the central structure?

Thanks for detailed method. I'll now get a chesire and sight tube. LED would be so useful.

About M82, I've only seen it twice. Call me a newbie. Using 24mm eyepiece. I would see it next time without fail using a barlow lens and look for central structure.

[jetstream]

Good stuff Ishan, you will see a small mottled area in M82 and this will show at moderate mags- a 2mm exit pupil is a favorite starting point for small ( in the EP) galaxies after I find them.

A OIII filter will really make the Veil stand out, and from your dark sky site it will be very good using your 24mm. Be careful which brand filter you choose as they are not all equal..... Lumicon and Astronomik are proven performers- in the scope and in testing.....

[Ishan Mair]

Thanks Gerry. I will note down your recommendations.