Helios 150 f8 achro Project - First Light!

[A McEwan]

I finally got a dark clear night (though patchy initially) to test the recently finished Helios 150mm f8 2Special" achro that's been mentioned before on this board.

When I was setting up at 9:45 it was through gaps in the cloud, however for once I decided to sit it out as I could still study Mizar/Alcor and M13 in the meantime.

So I spent a while admiring those views. M13 through the big refractor was pretty stunning, but I only got up to 52x on it as the cloud covered it up before I progressed through my higher magnifications. But even at that it was a lovely sight with pinpoint stars. I'm sure at higher power it would have resolved very nicely.

I was extremely nervous at slewing this great big tube around and it was a while before I became comfortable with it! If anything slipped while I was underneath it I'd have been knocked out I'm sure! Actually, while polar aligning, the single bolt that holds the dovetail to the mount head did slip but luckily I heard it and caught the tube before it slipped too far! I made sure the safety bolt was also tightened up after that.

I then hunted for Comet Garradd after locating and viewing M71 for a while and enjoying the definition and sharpness. Again, lovely view, and then by slewing East a degree and a half or so I saw the elongated fuzzball that is Comet Garradd. Very nice view, obvious elongation. Hard to see a definite tail. I would have reached for my OIII filter but was actually enjoying the view too much to bother!

Double cluster fit beautifully into the field offered by a 42mm Superview (65 degree cheapy) eyepiece with lovely pinpoint stars and obvious colour definition. M31 and its companions likewise, and also using the 23mm 84-degree Axion LX (not cheapy).

Finally I swung over to Jupiter, low over the horizon but in a better position by 12:30 when I started finishing off. Nice to see the old chap again and good that the SEB is back too - everything is right with the universe again! Now, I know what you're waiting to hear - how was the colour in that f8 6-inch achromat? Well.... I was using the Baader Semi-Apo filter, and apart from atmospheric chromatic aberation caused by its low elevation, there was none! Detail was good but made even sharper when I added a contrast-booster filter to the mix. I tried the view without the Semi-Apo filter too and noticed immediately that there was a tinge of chromatic aberation, so back the filter went and it was gone again! I used a range of Ortho's to study the big chap and found the views at 171x and 200x (7mm and 6mm) to be the best.

Overall it was very enjoyable (though nerve-wracking to start with) and I was impressed at just how good the views are through this 'scope. Jupiter will be getting a lot of study through it when it's riding higher in the sky.

Ant

[Neil English]

Hi Ant,

Great first light report. Thanks for posting.

These big achros pack a powerful punch alright. M13 looks beautiful through large, unobstructed optics. It's a pity you didn't get to crank the power up some more on it though. It would have been stunning at 120-150x!

It was also interesting to hear about your findings with the various filter combos. But just wait until later this autumn, when Jove will be very high up in an evening sky!

I'd be keen to hear how this instrument star tests for you in due course.

Regards,

Neil.

[A McEwan]

Hi Neil,

The star test is excellent. Perfect intra and extra-focal patterns, with a merest tad of undercorrection (if I'm interpreting it correctly). In focus evertything is just sweeeeet!

It's a good time of year to have a new telescope!

Ant

[John]

The star test is excellent. Perfect intra and extra-focal patterns, with a merest tad of undercorrection (if I'm interpreting it correctly).....

Sounds a really good objective Ant

It would suit a Chromacor O-1 exceedingly well - unfortunately the one I used to have is currently in Canada

I seem to recall that your scope is one of the older models - with a non-collimatable lens cell ?. Having owned one of a similar vintage and tried a couple of more recent ones, I have a sneaking suspicion that the older ones have slightly better optics.

They are big lumps to haul around though - I don't miss the effort to mount and unmount my 6" F/8's - the Meade AR6 was even heavier than the Synta ones

Thanks for the report

[A McEwan]

They are big lumps to haul around though - I don't miss the effort to mount and unmount my 6" F/8's

Funny you should mention that...

I'd used it a few times in daylight for solar observing (again, excellent) so was used to setting it up but not aligning on Polaris. Last night however was the first time I'd set it up and polar aligned in the dark! Big difference!

I put the tube in the rings in the horizontal position then added the accessories and balanced it in Declination, before swinging it up to "upright" to point to the pole star. I moved around to the focuser and there was a juddering sensation - the single knob securing the dovetail bar (a heavy WO one) wasn't enough to hold everything in poisition and the thing was slipping bit by bit through the clamp! That's when I realised the necessity of the safety bolt. With that tightened up in addition (with screwdriver!) everything was secure and I could breathe again.

Mind, it was a while until I was completely comfortable with swinging the great behemoth all over the sky!

Thje flexi dew shield helps with a reasonable mounting balance point, so that even views at the zenith were reasonably placed for me sitting on a small folding stool.

One thing I did slightly kick myself for though, was that the GSO Linear focuser requires extensions to reach focus a lot of the time. If I'd gone for a Moonlite I wouldn't need them...

Yes, it's the non-collimatable version that I have.

Ant

[southernman]

Great report. I always take an interest when they are about the performance of a big frac.

[SpookyKatt]

Nice report Ant, I'm glad it working out well for you

I always found that Helios to be an excellent scope

and it gave me alot of great views.

Kathleen

[Doley68]

Hello,

I have the bresser version of your scope and am interested to hear that you use a semi apo filter and like it, many people seem to be very negative about them but I think they should make a good addition to this kind of scope. I am planing on buying one soon.

Did you stack the contrast booster with the semi apo or on it's own?

[A McEwan]

I stacked the Contrast Booster - or rather, I added it to the eyepiece. The Semi-Apo was installed on the diagonal. I only used the CB when viewing Jupiter as I understand it does a lot to bring out planetary detail. The view with just the Semi-Apo was pretty good without the CB - only a small improvement with it in place. At that point Jupiter was only about 25 degrees above the horizond, if that.

Ant

[nightfisher]

really glad your getting on well with that big frac, out of interest what does the OTA with focuser weigh

[A McEwan]

I haven't actually weighed it, Fisher! I keep it in the shed and haven't had it handy for weighing - and it's pouring down here now! The flexi dew shield takes a bit of weight off (good option) so it's probably overall a pound or two heavier than the Equinox 120. I'll weigh it next time I bring it inside.

Only half-regret is that I didn't hold out for a Moonlite for it, but that would have been a big outlay that I didn't have the money for at the time, so...

I must admit I'm surprised at the negative comments on the Semi-Apo filter. When I started testing it on daylight objects, the difference was obvious and not subtle at all. I therefore had high expectations for night observing, and those expectations were met as well. It does NOT eliminate CA but it does a good job of making it inconsequential - to my eyes at least.

Ant

[PaulG]

Proper hairy chested telescope that, wish i still had mine.

Paul

[John]

really glad your getting on well with that big frac, out of interest what does the OTA with focuser weigh

I seem to recall my Konus 6" F/8 achromat (same OTA as the Helios) weighed around 20 lbs with the standard focuser and a 2" diagonal.

[nightfisher]

I seem to recall my Konus 6" F/8 achromat (same OTA as the Helios) weighed around 20 lbs with the standard focuser and a 2" diagonal.

Thanks john i will stick with my "pimped" 150 f5, a right nice widefield scope

[A McEwan]

Hairy chested telescope - I like that! But aren't all telescopes female?

Ant