Looking for a Complete idiots Guide for an 8' Travel Scope

[Davekyn (David)]

It seems there are many reviews and articles on the internet about the great innovations people have thrown together with regard to travel scopes. Unfortunately I am having great difficulty in finding any detailed plans or guides the depict with information that is easy to follow.

I'm looking for plans or a guide to building an 8" travel scope. Can anyone recommend a book for beginners...So i can work out how far to place the parts as well as methods to measure and put it all together...working out the mirror cell...counter weights...tension controls and so on.

Perhaps once I learn the basics of all those things, I can think about how to engineer something myself...or better understand some of the show cased designs on the internet...as it stands for me now...I have no idea what I am actually looking at, other than a portable truss dob.

The following briefcase scope is perfect as are many others:
http://www.cloudynights.com/item.php?item_id=1115
But there is so much I need to understand before I can attempt to embark copying what I see on that link or most of the ones I come across for that matter.

No sense getting any parts until I understand how it all works...where should I start?

[mercedes_sl1970]

You could have a look at these, not all with complete plans:

http://www4.in.tum.de/~stenzg/reisedobs.html

http://www.synrgistic.com/astro/telescopes/traveler.htm

http://home.planet.nl/~asuyker/nvws/...gDobsonian.htm

http://donscopes.webs.com/travel8.htm

Andrew

[Rod]

Hi David,

Not sure that you'll find the detailed plans you are after. Albert Highe gives a good explanation of several 3 pole designs here:

http://www.ultralightscopes.com/Links.htm

I built a 10 inch travelscope earlier this year. What I did was draw the parts out on a free CAD program. Another iceinspace member then kindly CNC routed the parts for me. It was pretty easy to build that way - almost like putting together a jigsaw puzzle. I had built a few dobs before so that experience certainly helped and Bruce spent quite a bit of time making sure he understood what I was trying to express in my drawings.

Can you say a bit more about what you are trying to achieve with a travelscope design? Airline carry on? Something to fit in a small car?

Those kind of parameters help identify what compromises you may need to make. Travelscopes are usually compromise instruments. You often take shortcuts to facilitate breaking it down into a smaller package. For example in mine the top of the mirror box unpacks and becomes the groundboard. It's compact but the scope feels a bit 'springy' when it moves as the groundboard is smaller than on a conventional dob. I also truncated the altitude bearings so I cannot observe below 30 degrees. Again this was to save space when loading it on an aeroplan.

Rod.

[Davekyn (David)]

Thanks for the links...I'll learn what I can so as to better understand the responses and ask the right questions when needed.

I like the brief case version as I'm looking at transporting the "parts" in the top half of a large Back pack (or lower half to top) to Hike with. I understand what you say about the compromises, however need to learn quite a bit in order to make the right decisions.

I really don't know what else to say...I guess a 2" focuser would be preferable for lower Mags? I just figure if I could better understand how the parts all work with respect to measurements and alignments...that might be a good place to start. I think the lack of lower altitude is not much of a big deal for what you end up with.

I'll go check those links and start learning...thanks again

[Davekyn (David)]

From what I can gather a good way to get started on parts for a travel scope project is to simply buy a dob outright?

I was looking at Andrews and considering the prices for a main mirror else where...it really does make sense...(if ones budget is tight).
Guan Sheng GS-680 8" 200mm x 1200mm
Question...I don't believe this model comes with a two inch focuser...BUT, do I really need one or is there any benefit to having one with an 8" scope for Wide filed of view.?

still going over those links.

[Rod]

Hi David,

Yes buying a cheap dob is an option for getting the parts. I would check ebay too. I just bought a mirror set there for my son so you might pick up something there.

You could get away without a 2 inch focuser- lots of people do. Personally I would always have one. My favourite eyepieces are 2 inch barrelled ones - because they do accommodate wider fields. That said a set of hyperions would work well on an 8 inch and they fit both barrel sizes.

Rod.

[Davekyn (David)]

Thanks Rod,
while Ebay or even any secondhand setup might be an option, the state of the mirror is very important to me. I have been using Ebay and have sold thousands of items to make a modest living with a 100% feedback. I have to say that in that time, I have also come across many people who sell items that arrive as NOT described. I guess you must of been lucky or prepared to settle for what arrived. In my exsperiance, unless I could actually view the item myself, I would be very hesitant in buying a mirror,secondary or any part off Ebay...I would much prefer to put my trust in someone here & even then I would be taking a leap of faith.

A very low price might make it atratcive I guess. If I knew more about mirror and could possibly improve the mirror, that might also pursueded me, but given I don't...I think my own experience with the Guan Brand of scope had been a very positive one, and I have heard so many people rave on about the quality of thier mirrors Vs price...so at the end of the day...I think a Brand New Untouched scope of that type would not only be quite fordable but help to give me a bigger sense of satisfaction and spur me on to look after the finish product that much more.

I do appreciate however, your mention of Ebay...I'm just not knowledgeable or confident enough to deal with the little niggles that commonly commonly arise from the sellers lack of disclosure. Unfortunately I find Ebay to be coming worse at this sort of things with each passing year. Perhaps as I have more experience and the means to address issues that might arise from such dealings, I would go second hand in a heart beat as I do with computer & electrical gear.

On the topic of Budget Vs Quality:

I was wondering the comparisons between the Budget
Guan Sheng GS-680 8" 200mm x 1200mm
and a completed mirror from:
http://www.telescopes-astronomy.com....#main%20mirror

200mm (8") Soda Lime f/4 Parabolic Mirror $340AUD OR $227US$
200mm (8") BK7 f/4 Parabolic Mirror $360AUD OR $235US$
200mm (8") Pyrex f/4 Parabolic Mirror $375AUD OR $245US$
200mm (8") Soda Lime f/6 Parabolic Mirror $340AUD OR $227US$
200mm (8") BK7 f/6 Parabolic Mirror $360AUD OR $235US$
200mm (8") Pyrex f/6 Parabolic Mirror $375AUD OR $245US$

F6 or F4 ???

I understand that buying my own mirror that I may be able to benifit from choosing a or lower F/R...the Guan dob is F6.
My previous 12"Dob was F5...I am not sure what the resultant outcome would be other than a wider field of view?
I did primarily use my dob for wide field DSO's...but I loved galaxies as well & wonder if F6 would be better at this????
I did not really appreciate planetary viewing such as Jupiter or Saturn as it was simply too cloudy or a washy look that had me constantly adjusting this or that with filters and so on...but if F6 will serve me better on the moon and galaxies I'd definitely consider that...would it be better on doubles as well?

I note that I would be missing a 2" focuser with the Guan Dob...holding me back from the wider field of view two inch Eps can offer at a more affordable price...BUT would an F4 mirror help minimise this concearn to some degree?...but then the compromise on F6 again to which I am unsure of...LOL...grrrrrr

Thanks again Rod and sorry for being long winded & picky as well. I do appreciate your input very much...could not make the right choices without your help.
PS.....I still wanted to talk about the "other" differences in those mirrors such as wave length & materials made out off.

[Rod]

Hi David,

You have more experience with ebay than me so I won't comment there.

In terms of mirrors, I would always go for the pyrex mirror. The manufacturer is more likely to have been able to make a quality product. Same thing with F ratio. F4 is much harder to make well than F6. In an 8 inch mirror I don't see many advantages with an F4. The F6 will have a similar wide field if you use a long focus eyepiece. If you build an F4 you will need a coma corrector and need to build a bigger mount to bring the eyepiece to a convenient height. I can't comment on the quality of these mirrors as I rarely buy mirrors. I still make my own. The ebay mirror is for a quick father son project. I didn't want him to lose interest waiting for the mirror to be finished.

When thinking about your design, make sure the top end is as light as possible. The Guang Sheng focuser may be a problem there. I would recommend the Kineopics HC 2 shown here:

http://www.kineoptics.com/HC-2.html

It's weight is negligible and it is a very good focuser. I use one on my Travelscope. Similarly use something like a quickfinder as a finderscope. It's also small and light.

I was thinking that a single pole design might be a good way to meet your requirements. Ross Sackett has some examples here:

http://www.stardazed.com/MyTelescopes.html

Chris (scopemankit) built a very nice single pole scope. There are photos of it on this forum somewhere.

Hope that helps,

Rod.

[Rod]

Hi David,

You have more experience with ebay than me so I won't comment there.

In terms of mirrors, I would always go for the pyrex mirror. The manufacturer is more likely to have been able to make a quality product. Same thing with F ratio. F4 is much harder to make well than F6. In an 8 inch mirror I don't see many advantages with an F4. The F6 will have a similar wide field if you use a long focus eyepiece. If you build an F4 you will need a coma corrector and need to build a bigger mount to bring the eyepiece to a convenient height. I can't comment on the quality of these mirrors as I rarely buy mirrors. I still make my own. The ebay mirror is for a quick father son project. I didn't want him to lose interest waiting for the mirror to be finished.

When thinking about your design, make sure the top end is as light as possible. The Guang Sheng focuser may be a problem there. I would recommend the Kineopics HC 2 shown here:

http://www.kineoptics.com/HC-2.html

It's weight is negligible and it is a very good focuser. I use one on my Travelscope. Similarly use something like a quickfinder as a finderscope. It's also small and light.

I was thinking that a single pole design might be a good way to meet your requirements. Ross Sackett has some examples here:

http://www.stardazed.com/MyTelescopes.html

Chris (scopemankit) built a very nice single pole scope. There are photos of it on this forum somewhere.

Hope that helps,

Rod.

[Steffen]

Originally Posted by Davekyn

Guan Sheng GS-680 8" 200mm x 1200mm
Question...I don't believe this model comes with a two inch focuser...

Hi Dave, in case you're still wondering, my son's got the GS-680, it definitely has a two-inch focuser. It's also dual-speed.

Cheers
Steffen.