Travel scope

[Brycepj (Peter)]

Hi everyone I would like some advice.
I currently use a 10" Goto dob however have found that it's a bit big for carting around when I go to holiday destinations where dark sky's are available.
I have been kicking around buying a scope that is portable and not difficult to set up and not expensive.
Goto function would be ok but the preference is not to go this way due to cost. The budget is $550.
I have been looking at 102mm maksutov made by Saxon or skywatcher, these sit on an EQ2 mount and appear to be fairly portable given the size and fit the budget.
Can anyone tell me the image quality as compared to my 10" dob?
What are the other options?
What scopes are others using for travel scopes.?
Would i be better off with a large pair of binoculars?
Thanks

[geolindon (Lindon)]

i dunno Pete,

i reckon when you get to the dark camping site you will really appreciate the 10" dob.

http://www.ebay.com.au/sch/Trailers-/66468/i.html

Lindon

[ZeroID (Brent)]

Lets be honest, nothing except something bigger will match your 10" DOB. That being said, in darker skies away from your usual LP'd suburban location a good smaller scope will give some outstanding views. I used my SW 80mm f5 refractor, my current guide scope on one holiday and being in a pitch black site was blown away by the view.
I suspect a refractor might be a better choice as the smaller mirror based scopes tend to be affected by the central obstruction syndrome of the secondary mirror. I used the Lunt 102mm f7 on one trip and it was awesome although it is a bit big for a grab and go.
And a decent pair of binocs should always be packed regardless of where you are going.

[barx1963 (Malcolm)]

Bryce
I assume the 10" is a solid tube? One option is to convert the scope into a travel scope. Here is the thread on my 8" conversion. http://www.iceinspace.com.au/forum/s...d.php?t=108905
Basically on this one the entire scope apart from the trusses pack into a small box. Based on a Gary Seronik design see here http://www.garyseronik.com/?q=node/206

Fairly easy to make if you have access to a router and jigsaw. And you can reuse the spider, focuser and finder.

Malcolm

[Brycepj (Peter)]

Thanks guys for your advice I have ordered a Sw 80/400 on an az3 mount.
Don't really want to convert my dob. I'm not that clever. If I had an old 8" or some one gave me one I might try it but not my 10".
Thanks again for your advice.

[Tamtarn]

I would have suggested this http://www.ozscopes.com.au/skywatche...telescope.html.
I have one and it works like a dream
Barb

[Brycepj (Peter)]

Thanks Barb
Looks like a good scope, may be a bit big being 650 as I,m looking at fitting the scope into a carry on luggage size bag
Peter

[julianh72 (Julian)]

Originally Posted by Brycepj

Thanks Barb
Looks like a good scope, may be a bit big being 650 as I,m looking at fitting the scope into a carry on luggage size bag
Peter

As others have suggested, for a carry-on scope, my pick of the best options would be a short-tube refractor (80 mm / f5 or similar), or a Mak (90 mm or so). A little Mak is even more compact than a 'frac (my 90 mm Mak OTA fits into a styrofoam-padded box that is about 350 mm x 125 mm x 125 mm), and they have comparable light-gathering capability and image quality, but the Mak has a much longer focal length / higher magnification, so which one is ideal for you will depend partially on what you prefer to observe.

Team either with a couple of eyepieces, a decent lightweight alt-az tripod, a star diagonal and a 45-degree erect-image diagonal, and you have a very portable, very versatile telescope for both daytime terrestrial use and night-time star-gazing.

(It should go without saying that you should also pack a pair of binoculars.)

[Brycepj (Peter)]

Thanks Julian
Decided to go with the Sw 80/400 on az3 mount. Mainly because it's an f5 and I like the idea of using it as a guide scope down the track. My Dob is an f4 so although I don't get the same mag. Or light gathering Images should be good quality especially using Televue plossl Ep's( I will do a comparison from a newbie perspective )
I always carry my 10 x 50 binocs wherever I go.


I noticed that you have a zwo camera in your tricks can you tell me your opinion why you decided on this camera, pros and cons etc. I have read reviews which all sound great I would value your 20c
Regards
Peter

[Brycepj (Peter)]

Following on from the below post can anyone tell me "what happens when you push the mag. Up beyond a scopes capability". ? Am I correct in the assumption that you won't be able to obtain a clear focus? Or unable to focus at all?
Let's say using the sw 80/400 f5 and I use a 6mm Ep in a 3x Barlow.would that work.?
Peter

[barx1963 (Malcolm)]

Originally Posted by Brycepj

Following on from the below post can anyone tell me "what happens when you push the mag. Up beyond a scopes capability". ? Am I correct in the assumption that you won't be able to obtain a clear focus? Or unable to focus at all?
Let's say using the sw 80/400 f5 and I use a 6mm Ep in a 3x Barlow.would that work.?
Peter

Very good question Peter
For any given scope, there is a limit to which the magnification can be pushed before the image deteriorates. Often that is given as 50x per inch of aperture. But that is a theoretical limit, meaning that it assumes perfect optics, perfect collimation, perfect seeing. Given all those factors it may be possible to push a 3" scope like yours to 150x, but the combo your are suggesting gives a power of 200x (400/6x3).
Essentially, the more magnification you use the more you are also magnifying the atmospheric distortions. Also as you magnify you reach a point where you make the image larger but the resolution limits of the scope (which is mainly a function of size) means you reveal no more details. This is known as "empty magnification".
Experience tells us that 10x or 20x per inch is more useful. So the 67x revealed by your 6mm EP is more likely to give satisfying results.

Cheers

Malcolm

[Brycepj (Peter)]

Thanks Malcom
This does clarify my question.
Can you explain "f" ratio in telescopes
The lower the f ratio is better, which has been my understanding, if you have a low f ratio how does this relate to the clarity difference under various magnification levels.
Is this logical or do I have my wires crossed. Is a good scope a balance of these variables?
Is it dependant on what you wish to observe, which means different scopes for different applications? If this is true what is a good all round scope.? Is object luminosity, aparent / actual magnitude the guiding factor?
Sorry if this is getting deep it's just my inquisitive nature, that's why I love star gazing

[barx1963 (Malcolm)]

Originally Posted by Brycepj

Thanks Malcom
This does clarify my question.
Can you explain "f" ratio in telescopes
The lower the f ratio is better, which has been my understanding, if you have a low f ratio how does this relate to the clarity difference under various magnification levels.
Is this logical or do I have my wires crossed. Is a good scope a balance of these variables?
Is it dependant on what you wish to observe, which means different scopes for different applications? If this is true what is a good all round scope.? Is object luminosity, aparent / actual magnitude the guiding factor?
Sorry if this is getting deep it's just my inquisitive nature, that's why I love star gazing

"f" ratio is simply the ratio of focal length divided by aperture. So your 80mm scope is 400/80 = f5.
It is not correct to say that lower f ratio is "better", it can have some advantages and some disadvantages.
For example in a newtonian scope, such as a dob, with a long focal length will have the eyepiece well off the ground, in a large scope, you need a ladder to observe most objects. On my 20" f5, I stand on the third step of my ladder to observe a lot of the time. If I bought a shorter scope, say an f4 20" I could start observing most objects from the ground and only need a small ladder, but the following would need to be taken into consideration:
- the image would display more coma, probably requiring a coma corrector
- the scope would cost much more, cost increases substantially as the f ratio gets smaller.

The lesson is that as in most things there is no absolute, every decision in scope design is to some extent a compromise.

Malcolm

[Brycepj (Peter)]

Thanks Malcom
So my 10" 1200 f4.7 dob is a good compromise, (and no ladder.) ever time I use it the images just blow me away.

[gaa_ian (Ian)]

Hey Peter
I have scopes from 100mm refractors to 10" Dobs, Go-TO's and MCT's to play with. My 10" Dob is my favourite, but I use my 4" Kson travel scope much more (as I travel a lot)
I am looking forward though to getting a bit more time outside with the new 6" RMCT from Bosma. Especially for planetary nebula and the planets, where I think it should excel !
Even with a Go-To mount the whole set up comes in under 20KG (not exactly hand luggage though)
Cheers Ian

[julianh72 (Julian)]

Originally Posted by Brycepj

I noticed that you have a zwo camera in your tricks can you tell me your opinion why you decided on this camera, pros and cons etc.

Firstly, please note that I am VERY new to digital astro-photography. I played with film astro-photography many years ago, but have only recently (12 months) got back into astronomy and astro-photography, so my experience (and budget!) is limited, and my equipment and skills are very modest.

I bought the ASI120MC because it seems to me to be unbeatable in terms of resolution, sensitivity and versatility for the price - currently showing as US$279 plus US$20 postage: http://www.zwoptical.com/Eng/Cameras/ASI120/index.asp

It is FAR more sensitive than the other cameras I found for less than about $500, and it can take quite long time exposures (plenty long enough for my humble mount to track!), so it can be used for DSOs as well as solar system and lunar use. (And it can be used for daytime terrestrial photography as well.)

Note that most "eyepiece cameras", including the ZWOs, have quite small sensors, so it has a narrow angle of view when fitted to a telescope focuser, so it may not be ideal for capturing the bigger DSOs or the whole of the Moon, unless you have a very short-focal length telescope. With the three telescopes I have available to me, the effective field of view on the ZWO are as follows:

Meade LX90 200 mm SCT: 0.10 deg x 0.14 deg
90 mm Mak: 0.17 deg x 0.23 deg
Celestron NexStar SLT 130 mm Newtonian: 0.32 deg x 0.42 deg

Even the 650 mm focal length Celestron can't capture the whole disc of the Moon, for example.

There are lots of planetary / solar system imagers that you can pick up for under $100 or so, but these won't work well (if at all) for DSOs. For example, I bought a cheap planetary imager from eBay and it works well, but I found the fact that it can't do long exposures, and doesn't have the sensitivity to capture DSOs to be a big restriction for my interests. I think the cheapest alternative would be the Orion StarShoot All-In-One Astrophotography Camera which you can get for about $549, although there may be others that I have missed.

I really like the fact that it ships with a 150-degree wide-angle lens, so you can use it for all-sky imaging without a telescope - make time-lapses of the night sky, capture meteor showers, etc. You can also buy cheap CCTV lenses that will fit it, so you can set it up for other uses too.

Other nice features are that the camera body has a standard M42 thread and a 2" body, as well as a screw-in 1.25" adapter, so it can fit easily to just about any equipment you own - it's a really nice piece of design. The body is milled from a single piece of aluminium, so it feels like a real quality product. It also has an interface for auto-guiding, so even if I ever acquire more sophisticated astro-imagery gear (which I doubt), it would still be a useful part of my kit.

I have found it very easy to use, and it works well with a variety of capture software. I am just getting started (I wish the night sky in Brisbane would clear up for a while!), but early results have been very promising!

All in all - highly recommended as an entry-level astro-camera!

[Camelopardalis (Dunk)]

With the scope being only 400mm focal length, that sensor would give you almost 1 x 0.75 degree FOV across, so could be an interesting experiment!

If you wanted to try planetary imaging, it should work well (with a suitable Barlow) in your Dob too.

It just depends what your imaging interests are. For DSO imaging, I'd suggest considering a entry-level DSLR like a Canon 1100D or similar.

[Brycepj (Peter)]

Julian & "dunk"
Thank you so much for your detailed information, I am just a real newbie however I do take pix of 20 to 30 seconds using my nikon D5100 using eye piece projection. Yes they are fuzzy for real detail but a great leaning experience which I will preserver with, have not looked at "stacking" images yet as not sure not computer can handle it. Basically the DSLR and adapters etc work well for star and planets plugged in to the Goto dob. It can be frustrating get focus etc but the pix even fuzzy are well worth it.
Eventually I will have a full blown astro photography set up so its a matter of building the equipment list slowly. The zwo looks like the next way to go.
You may have picked it up in other posts but the intention is to convert the Dob to an Eq5 or eq6 pro, using the 80/400 as a guide scope pluging in the zwo would probably give me a good basic set up for astro pix. I suppose you could say it's like building your dream home.
No doubt I will post more questions as the funds are available to buy moe gear and "er in doors" doesn't have too much objection.
Still keen on Big Dobs though especially SDM telescopes look so impressive....ah it is to dream

[ZeroID (Brent)]

Just FYI the little ZWO is also perfect for Peltier addition so you can supercool it for longer exposures. A TEC and external radiator plus some insulation gives me -2.5 C from ambient 24 C, a significant reduction in sensor noise.
It is also Ha sensitive when you remove the IR cut filter on the mc (colour) model. Just unscrews. Very adaptable and clever little camera and good value for newbies who want to experiment without getting into the big budget hardware.

[Camelopardalis (Dunk)]

Ah so you already have a DSLR...in that case, just get yourself a flattener for your 80mm and you'd be good to go for wide field.