Travel Scope Project

[Rob]

Guys,

I need a travel scope (on a budget) to come with for Mars & Lunar eclipse viewing. I had an idea of picking an old M42 thread 500mm Mirror lens and then attaching a T2 thread 1.25 Diagonal to it (maybe an old ETX one??)... do you think this will work?.

Just a little worried about distance to EP and if a barlow would work ok off the back of this setup?.

Any advice would be great.. have you even done this?.

Rob

[RT65CB-SWL]

Hi Rob.

I had a similar idea during 1999 for viewing the solar eclipse in BG ?? when I used to own a 200mm @ f4 telephoto lens (Vivitar) and a 2x matched multiplier (also Vivitar), therefore the focal length and f/ratio doubled. At the time I only had my TeleVue Ranger (70mm/480mm @ f6.8). 

I did try some 'test' photo's about thirty to forty minutes before first contact, but I found the image scale was to small for my liking. I had used a Mogg Pentax K to 1.25" adapter, the TeleVue star diagonal from the Ranger, a Beacon Hill Telescopes eyepiece projection unit, my TeleVue 8mm & 15mm Plossls and a Thousand Oaks glass solar filter. 

I took the TeleVue Ranger too and took it and the other astro equipment, as above, in an aluminium case on the aeroplane, (Tupolev TU-154), as 'carry-on' and just fitted under the seat. The camera, (2x Pentax ME Super), camera lenses, tripod & head plus other photo accessories were packed in my suitcase for the hold.

I think the best thing is to try it before and you decide. Like I said my images were to small for my liking. So I decided on using the Ranger etc for photographing the eclipse. As they are on 35mm slides I have not had the time to scan and have digital copies to show here. 

 

[Rob]

Thanks for the reply. This in part is my dilemma. I have my Starwave 70ED F6 that could poss cover the situation, just worried everything (Both Mars & Moon) will be very small on visual & photography.. the Moon less so of course.

 

[Louis D]

There won't be enough back focus with the telephoto lens to use an eyepiece and a diagonal with it.  It might just work with the eyepiece alone.

Consider building a travel Dobsonian telescope like I described in another post to someone else looking for large aperture and portability on a tight budget.

[Astrobits]

I agree with Louis. There will be insufficient back focus for a diagonal.

In the 80's I had a Tamron 200-500 zoom lens. I glued a tube onto a spare rear lens cap to hold an eyepiece and it worked a treat. It was fascinating to see nebula appear as if from nowhere as I zoomed from 200 to 500 mm. Because the f ratio stayed the same the actual aperture in use grew as the focal length thus making nebula easier to see.

nigel

 

[Stub Mandrel]

I have a RACI eyepiece, probably about 10mm, that fits a vivitar mount. I used to use it with a 500mm cat lens. to be honest it was disappointing.

[Louis D]

I experimented in the mid-90s with a 100-500mm telephoto lens and an eyepiece.  To attach the eyepiece, I bought a 25mm manual extension tube and some PVC pipe adapters to get from the roughly 2" outer diameter of the extension tube to the 1.25" inner diameter needed to mount the eyepiece.  I used nylon screws tapped into holes around the circumference of the adapters to hold everything together.  It worked pretty well for such a kludge.  It was tough on the neck and back, though.  It was neat to experiment with various zoom settings and aperture settings.  On the Orion nebula, closing down the iris would sharpen up the Trapezium I found.  It made the nebula dimmer, but the stars came to a more pinpoint focus.  Within a year, I had bought my first scope; and the rest is history.