Helios 150 'Special' observations

[A McEwan]

Somebody recently asked how things were going with the Helios 150mm f8 refractor that I bought and did some work to in the summer. I hadn't mentioned it for a bit, having been concentrating on my 90mm Celestron/Vixen f14.4, so the last couple of nights I've had the 'Special' out in the garden for Jupiter and the Moon.

Rest assured, there is nothing bad to say!

Both nights have had average or slightly better seeing, and the Moon has been waning gibbous. Jupiter has been the main target on both occasions. The scope is used with a Baader Semi-Apo filter permanently installed in the 2" dielectric diagonal and I've only been using Baader Genuine Ortho's. (I'm still waiting for my Baader endorsement cheque... hint, hint....!)

Seeing last night limited the magnification to 171x tops, with the best views at 133x. There were no spots or barges visible, but the moons were easily brought to sharp discs so I was confident that I was seeing all that it was actually possible to see using my equipment that night. When I turned it to the Moon, I was rewarded with some very sharp terminator exploration, with a razor-sharp limb and mountain peaks I nearly scratched my eye on!

Tonight was better. The seeing allowed occasional views at 200x (6mm) on Jupiter, with the best being seen most consistently at 171x (7mm). All the belts were visible, with the temperate belts being most easily seen at the lower power. A dark barge was very evident in the NEB, nicely elongated so that there was no confusing it for a shadow transit at all. Continued viewing showed that as it passed the meridian the GRS begen to approach it in the SEB. Very pale, the contrast between the two features was most striking. The GRS - the most famous storm system in the solar system - would easily have been overlooked by comparison with this new dark upstart barge in the northern hemisphere!

Swirls and structure were to be seen in the SEB and NEB as well. The view was not completely CA-free, though the Semi-Apo filter does a fantastic job of taming the colour. I could easily have continued observing with just the Semi-Apo filter in place, but decided to install an 82a light blue filter in the eyepiece. This completely removed the last vestiges of false colour and made the belts stand out a little more easily too. Consequently the storm features were also a little more evident, so I kept using the additional filter for the rest of the two-hour session.

I find the 82a to be a really useful filter. It seems to enhance contrast very nicely and as I said, what little CA is left over from the Semi-Apo filter is completely removed by adding it to the eyepiece. It has to be said, though, this slight CA is only evident on the limb of the Moon and on Jupiter.

Swinging to the Moon tonight showed very impressive views, but I did not linger as the cold and encroaching dew were beginning to get to me. I did get a chance to try for Plato craterlets, and managed two at 171x but I was not making a very serious attempt. Hey - I wasn't even sitting down!

These sessions have filled me with confidence that the performance of the scope is pretty good. These have been the very best Jovian views I've exp[erienced with my own equipment, so I have nothing to say against the Helios. To me, it is indeed quite 'Special'.

Ant

[John]

Excellent report Ant

Sounds like the Helios is living up to it's "special" label.

The dark, elongated barges have become a really distinctive feature of the NEB this opposition - much easier to spot than the, rather misnamed at the moment, Great Red Spot

Thanks for posting

[southernman]

Great post. It's good to know the big 'frac' is performing well.

[nightfisher]

Nice report Ant, bout time you used that lovely scope after all the hasle with paint cans, still cant believe your selling the equinox, but then you have that lovely carbon scope to make do with

[A McEwan]

Sale is pending on the Equinox. "Making do" won't be too hard, Jules!