First outing with a new ES 16mm, 68-degree MaxVision

[kev100]

Hi,

I got a new 16mm MaxVision EP at the weekend, just in time for what the forecast said would be the first clear night in ages. Although the moon was set to rise at about 8.30, I couldn't resist getting the scope out to compare the new EP with my Revelation plossls. Despite the poor seeing (due to the moon rising and some thin hazy cloud which appeared as soon as I got set up) first impressions of the 16mm were certainly pretty good. I noticed the larger fov immediately, and stars were pretty sharp and crisp to the edges. I checked out a few simple targets (M52, 13 and 92, Alcor/Mizar, Double cluster in Perseus), and, despite the lack of contrast in the sky, they all looked great. The EP seemed to perform very well with the Revelation 2.5x barlow, too; which I was very pleased about.

I swapped in my 20mm Revelation, expecting to see a noticeable lessening in the quality of the view, and was very surprised to find that it looked okay ... (!) I rechecked all the previous targets with the 20mm (and then my 9 and 32mm EPs), and they all looked fine. With only a little (barely noticeable distortion at the edge of the fov ...). 

It took me a while to work out what was going on. When I thought back to recent sessions with the Revelations, on moonless nights with relatively good seeing conditions, the fov pretty much wherever I looked was full of stars, and the distortion at the periphery was clear and distracting. On Saturday, however, because seeing wasn't very good, most of the stars I'd seen before were lost in the haze/light of the moon, with only the brightest and clearest visible. I reckon the poor sky/seeing levelled the playing field somewhat, so I'll have to wait for a proper dark night to really see the benefit.

The moon looked amazing, though!

Cheers,

Kev.

[happy-kat]

I find it really nice on m42 the moon and jupiter

[kev100]

HIya. I did spend quite a while with it looking at the moon, and was very impressed with the clarity and sharpness. And yes, I can't wait to have a go on M42 and Jupiter!

[John]

Interesting report. Your scope is fast (F/4.7) so will be a challenge for wide field eyepieces for two reasons, i) the eyepiece could show some astigmatism towards the edges of the field and ii) even if the eyepiece is sharp to the edge the scope will be generating some coma which will still distort the stars towards the field edges. You may well be seeing a mixture of these two aberrations of course !

The narrower field of view of the Revelation plossls could well show less coma and less astigmatism becuse they are just not showing so much of the off axis light cone.

I guess a coma corrector would clean up the outer parts of the field nicely but it's more £'s to spend and another optical item to install of course.

[kev100]

Hi John,

Thanks for the feedback. I guess I'll have to wait for a darker/clearer night to really compare the EPs. For now, I'm holding off on a coma corrector for both reasons you mentioned.

Kev.

[happy-kat]

Could a simple apperature mask do the same thing as a comma corrector just for visual use?

[John]

Could a simple apperature mask do the same thing as a comma corrector just for visual use?

Well it would turn the scope into a slower scope and would reduce eyepiece astigmatism. Not sure about coma as that is inherrant in the mirror figure. The downside is that it reduces the aperture of the scope though.

[happy-kat]

Off to read up how an expensive comma corrector works :-)

[spaceboy]

I have found seeing and transparency play a bigger part in astronomy than I had originally thought when first getting in to the hobby. This is why I prefer to read reviews that are side by side shoot outs as apposed to those over several sessions. The trick with any new kit is to give it the benefit of a good clear steady night which I know can be few and far between here in the UK.

[kev100]

Hi Spaceboy,

Totally agree about seeing being most important, and I can't wait for the opportunity to compare the MV against the plossls on a proper dark and clear night (hopefully soon!)

Kev

[Reeny]

My 16mm lives in the Revelation 2.5x Barlow.

They work well together.

The Barlow seems to clean up the abberations for me,

and the magnification works well on the 200P dob. 

(165x at an estimated 2.2x magnification)

It's also a nice size and weight compared to the other eyepieces I own.

It fits in a fleece pocket on cold nights.

[kev100]

Hi Reeny,

I was pretty impressed by how well the EP took to the barlow (albeit in a short observing session). It looks like I've got full cloud cover for at least the next week so it'll be a while before I can do a proper test.

Kev.