Review Skywatcher Startravel-120 OTA / Großfeldrefraktor 120mm 600mm f/5

 

Dear Karl,

 

It is 02:55 am and I just came back from a long observing session with the Skywatcher refractor. You wanted my feedback so here goes:

 

This telescope is perhaps the most portable rich field telescope that can also satisfy the need for a large aperture. Even though the 152mm F5.9 achromat has more light grasp and a longer focal length, it is more than twice the weight and having tried the TS152mm f5.9, the Skywatcher 120mm f5 and refractors of 100mm, 90mm, 80mm, 70mm and 60mm, I can attest to the fact that if you have to drive to go to a dark site, the best scope to take with you which will satisfy your needs for wide field viewing, is definitely the SkyWatcher 120mm f5.

 

I tried it this evening with Nagler 31mm, Panoptic 27mm, Ethos 21mm, 13mm and 8mm. The eyepieces that were a great match for the telescope were the Ethos 21mm and 13mm, yielding:

 

 - Ethos 21mm - 29x magnification, 3.46 degrees True Field of View and 4.2mm Exit pupil

 

 - Ethos 13mm - 46x magnification, 2.13 degrees True Field of View and 2.60mm Exit pupil

 

Although the Nagler 31mm yields a larger exit pupil (6.2mm) and a larger field (4.01 degrees), it was too bright due to large exit pupil and will be used solely with my filters.

 

Now, I was quite aware of what I was buying from you. The telescope of course suffers from field curvature as it is a very fast scope and does display slight coma. Note that the last 20% of the field of view is slightly out of focus from the centre of the field in 100 degree Apparent Field of View eyepieces. The Panoptic displayed much less field curvature and much less coa, but did not show the contrast and clarity of the Ethos. Bright stars of course display some chromatic aberration. 

 

All 3 characteristics of this scope (it is a short focal length achromat after all) are within acceptable range and an acceptable trade-off in exchange for the light gathering capacity, the crisp stars over a large field (I would say that 3 degrees is about perfect a field with negligible field curvature and coma in that circle of 3 degrees), the unobstructed views of a refractor and the excellent contrast displayed.

 

I "unfortunately" managed to observe only for 2 hours, as most of the time people were crowding my telescope and cruising the Milky Way, all the way from Sagittarius to Cygnus!!! We have wonderful views of various nebula (M8, M20, Ring, North American, Veil), a lot of dark nebula which were just standing out as patches of darkness against the rich star fields of the Milky Way (both Sagittarius and Cygnus are packed with them), lots of clusters (every single cluster visible in Sagittarius, M4 and M13) and also a few galaxies (M81, M82 and M51).

 

This telescope will be a lot of fun this summer. I have changed many refractors, all of which I liked. This one though, I am falling in love with it. With the changes we made (internal flocking with matte paint, upgraded rings and new focuser), the telescope performs excellently. Paired with the dual axis mount and tripod I have from a previous order from you, the whole system was extremely stable, with no vibrations at all. I plan to enjoy this scope for a long time to come and also to pair it with other scopes, e.g. mount the fantastic Skywatcher 102mm Maksutov Cassegrain you also supplied and chase both wide fields and double stars at the same time.

 

Considering also that with my binoviewers and Baader Herschel Solar Wedge the telescope displays a crisp image of the solar disk with granulation readily visible on about 35% of the solar disk, this telescope will get a lot of use both during daytime and night time. Also considering the low cost of the scope and even factoring the cost of mounting it, it is still one of the best propositions out there for a visual observer who wants a Rich Field Telescope.