ISTAR Scope Question

[michael]

I'm considering the purchase of an ISTAR refractor within the next few months and have a few questions.

I currently own an ES AR152 f/6.5 achromat which I enjoy a lot, but I would like something with better color correction for planetary use. I also own a Celestron Omni XLT 102 f/9.8 achromat and find the amount of CA in that scope to be perfectly acceptable, even unfiltered, it just doesn't have enough aperture. The 2 ISTAR refractors I'm considering are the Perseus 150-10 and the Asteria 150-8 R35. Now for my questions:

Would these scopes give a big improvement in color correction over my current f/6.5 achro?

How does the color correction compare between the 150-8 R35 and the 150-10?

Will an Atlas mount be sufficient to mount these scopes for visual use?

Would the cradle and dovetail on my AR152 fit these scopes?

What is the best way to purchase an ISTAR? Can you purchase directly from ISTAR? How long is the usual wait time?

Thanks in advance, I know this is a lot of questions. 

Michael

[istarmullet]

If you live is San Diego you can take a look through my Perseus 150 f15 to see what level of color there is...

[michael]

I live in Memphis, but thanks for the offer.

[Kitch101]

My Istar Perseus 150F10 showed a good image of the moon, albeit with some color fringing, DSO were no problem but on very bright stars it displayed lots of color, so much in fact that the Airy disc was difficult to discern. Using a Baader SemiApo filter brought good results and made for very good Lunar views.

The Perseus was a well built scope but I bought it due to the promise of the Raycorr being available soon, I eventually sold the scope.

I think a 150mm F10 Istar needs at least a G11 mount due to the long length of the tube and the large moment arm such a long and rather heavy assembly generates. I know that for visual people will use a smaller mount but then you are at the mercy of breezes etc affecting the stability as well as the extra wear and tear on the mount gearing caused by the increased inertia of a long heavy scope.

An F10 scope should be quite an improvement over an F6.5 in its control of extraneous color.

I settled on a 120mm 900mm fl top shelf apochromat and am very happy with it.

[michael]

Thanks for your response. Looks like the 150-8 R30 would be the best choice for the Atlas. I've also been considering the ES 127mm triplet and I don't really see many advantages to the 127 R30 in comparison; especially when the ES127 can be had for less money than the 127mm R30. However, I was thinking that the step up to a longer focus or R30 150mm might actually be worth it for the extra light grasp. I don't mind some CA, but even with a Fringe Killer or Semi-Apo, the AR152 shows a lot of CA on Jupiter and Saturn.

[Kitch101]

Jul 17, 2013 20:36:13 GMT -5 michael said:

Thanks for your response. Looks like the 150-8 R30 would be the best choice for the Atlas. I've also been considering the ES 127mm triplet and I don't really see many advantages to the 127 R30 in comparison; especially when the ES127 can be had for less money than the 127mm R30. However, I was thinking that the step up to a longer focus or R30 150mm might actually be worth it for the extra light grasp. I don't mind some CA, but even with a Fringe Killer or Semi-Apo, the AR152 shows a lot of CA on Jupiter and Saturn.

I think you can't get away from the fact that an achromat will show color on Saturn and Jupiter and brighter stars. I assume the R30 has been optimised to a different point and may show less violet at the expense of the red end of the spectrum. The extra inch of aperture will certainly be a big plus.  But these are big scopes so don't underestimate the size of mount for your specific needs.

Some of the new Chinese triplets are apparently performing very well in the 5" and 6" sizes, so do your homework before shelling out the $$$$

As an aside, I have a 135 year old 3.5" f15 scope that shows almost zero CA on Jupiter, as well as being a nostalgic experience!

Good luck with your choice.