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VMC95: a cheap and easy to use "astrograph" for not so large objects

astrophotography equipment
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#1 Hesiod

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Posted 17 March 2019 - 08:40 AM

The Vixen VMC95L is a flat-field modified Cassegrain, sold by Vixen; it is a sort of scaled down, low end version of their VMCs (20 and 26cm), which are designed as long-focus astrograph.

At 30cm long, 2kg heavy, the VMC95 can ride any light mount; the built-in flip mirror is a great help if the VMC is used with non-goto mounts (or with mounts whose goto capabilities are not much reliable), but also with goto mounts to adjust the frame; and while it focuses by sliding the primary mirror, my sample is totally free from mirror shift, which is noteworthy in a such low end product.

 

Unlike most other 3.5-4" CATs, the VMC95 features a rather large image circle, as can be seen by this master flat I took on an aps-c sized sensor

gallery_215679_10941_353191.jpg

 

The field of view is rather flat, but not well corrected for coma; also, instead of the spikes there are fan-shaped "mists" which are in my opinion much worse to behold:

gallery_215679_10941_1997492.jpg

 

Probably even a skilled photograher will have a very hard time to get APOD-level pictures with the VMC, but for those in tight budget, with small mounts and simpler cameras (APS-c or smaller sensor) at 220€ it may be a decent option to take "instagram-level" pictures of galaxies and clusters

gallery_215679_10941_369411.jpg



#2 petert913

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Posted 17 March 2019 - 09:08 AM

That's some nice resolution for a little 4" scope !



#3 Augustus

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Posted 17 March 2019 - 09:13 AM

My girlfriend had one of these and I used it. While you're right about the image shift, collimation was impossible and it had about 1/2 wave of spherical aberration. I gave her a 4" Orion Mak with a chipped primary which far outperforms it.



#4 Hesiod

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Posted 17 March 2019 - 09:31 AM

It was likely a defective sample or, if second-hand, had been badly abused by the previous owner/s (maybe they did something to the secondary assembly).

I would never purchase a second-hand VMC95 or 110 without the possibility to star test it because think its design is both more complex and less "safe" than spot Maksutovs'; however I have came to the conclusion that the VMC95 is superior to low-end 3.5" or 4" MCTs because of noticeably better low-power performances, far better photographic capabilities and very close high power performances.


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