Comments on Sky&Telescope 12" Dob Review.

[Satchmo]

Les and I have had a phone conversation and covered many topics including the purpose and `scope' of this particular telescope review and I must say it was interesting and educational to hear Les's views and methodology on amateur astronomy journalism and the telescope review process.

We have discussed the history of his mirror. I had offered this production mirror to Les, which I had earmarked for a personal project due to the non-standard focal length it had arrived at, after reading his 'Wanted' ad in an astronomy magazine for a similar focal length mirror. The lead time was six weeks to have it aluminised. Looks like every mirror no matter what focal length has someone's name written on it

I can understand its not the place or concern of any single telescope review to issue caveats or judgements about the optical consistency in general of particular product lines .

Regards

Satchmo

[ngcles]

Hi Mark & All,

Thanks Mark for the clarification.

And BTW, in addition to the one I own, I've looked through maybe half-a-dozen 'scopes with Mark's mirrors (including two owned by close friends who purchased from Mark on my recommendation). They all proved to be without exception, superb performers. The one I'm fortunate to have is a representative example of high standards he sets in all his optical work.

That is exactly why I used it as a reference against which to measure the review telescope which was a random choice I picked out of a palette load of cartons.

Best,

Les D

[Alchemy (Clive)]

thanks to les for his honest opinion and time to reply, both articles were an interesting read, and it gives a basic idea of what to look for, particularly for those who may not have the technical expertise of an expert mirror maker such as Satchmo.

cheers clive.

[Satchmo]

Originally Posted by ngcles

That is exactly why I used it as a reference against which to measure the review telescope which was a random choice I picked out of a palette load of cartons.

Thanks Les , that is high praise indeed. I think unconciously or not, people do read reviews with a desire to know what they may find when they might purchase one. Having studied scopes in the field and on the bench for years and discussing the experiences and owner opinions of others, there is clearly some optical quality variation evident in these low-cost scopes.

While it may not be the place, or responsibility of a magazine product review to issue caveats, it does go without saying that ` the individuals experience with a reviewed product may vary', particularly so on the budget end of optics.

[ausastronomer (John Bambury)]

I have looked through a couple of dozen different GSO and Synta dobs over the last 8 or 10 years. Originally the GSO dobs were sold under the Orion label. At that time Synta were sold under many different names. Back then the Synta dobs left something to be desired, optically and mechanically. The GSO dobs also improved rapidly in a short space of time. When Orion changed their generic manufacturer from GSO to Synta (2001 maybe ?) the Western world quality control standards quickly ensured the Synta scopes improved dramatically in a short time. It has only been in recent times that the mirror quality of the Synta scopes has equalled the GSO scopes. Simply because GSO had the benefit of Orion USA's intervention long before Synta did.

For reference Les just about all of the GSO scopes use BK7 as the primary mirror substrate. Not float glass or pyrex. Whilst BK7 is generally used for refractive optics, it does a very good job as a front surface reflective substrate. It sits between pyrex and float glass in its thermal and expansion properties.

These scopes from either manufacturer represent excellent value for money.

The one area that I have found where "both" can be improved dramatically in performance, is in proper internal baffling. This is a very simple DIY task and once these scopes are properly baffled they perform exceptionally well.

Cheers,
John B