Sumerian Alkaid, the scope that never was.

[Scooot]

Hi All

it is Friday afternoon, time for a few ramblings on the Sumerian Alkaid?

I cannot comment on the flex experienced by Dan.

The 'scope that I have appears rigid enough to hold a decent collimation with all my EPs including the 31 Nag and TV Paracorr combination. Movements are precise and vibration damping was not an issue at x160 (excellent views of Stephan's Quintet and NGC 891). I haven't gone to higher magnifications yet.

It is a lightweight and extremely portable scope and does (will) not have that truly solid/rigid feel of the heavy weight dobs.

An equivalent is the Obsession 15" UC. The cost of this, with box and optional(!!) secondary dew heater this is ~ $5500 => £5500 after shipping, VAT, duty etc. This is about £2000 more for a 'scope of 1" less aperture.

BTW, the mirror spec. I have is from Orion Optics and the Zygo gives 0.984 Strehl (Obsession guarantee >0.9).

I sincerely hope that there are more, positive experiences of Sumerian being recounted in the near future

This maybe the end of my Friday ramblings...or not.

Cheers

Paul

Hi paul,

It's great that you're so pleased with it.

When I receive my Canopus, one of the things I'm planning on doing to test how well the optics hold in place,is to see if the red dot of my laser moves as I move the scope through different positions. I can do this in daylight of course.

[niallk]

Hi All

it is Friday afternoon, time for a few ramblings on the Sumerian Alkaid?

I cannot comment on the flex experienced by Dan.

The 'scope that I have appears rigid enough to hold a decent collimation with all my EPs including the 31 Nag and TV Paracorr combination.  Movements are precise and vibration damping was not an issue at x160 (excellent views of Stephan's Quintet and NGC 891).  I haven't gone to higher magnifications yet.

It is a lightweight and extremely portable scope and does (will) not have that truly solid/rigid feel of the heavy weight dobs.

An equivalent is the Obsession 15" UC.  The cost of this, with box and optional(!!) secondary dew heater this is ~ $5500 => £5500 after shipping, VAT, duty etc.  This is about £2000 more for a 'scope of 1" less aperture.

BTW, the mirror spec. I have is from Orion Optics and the Zygo gives 0.984 Strehl (Obsession guarantee >0.9).

I sincerely hope that there are more, positive experiences of Sumerian being recounted in the near future  

This maybe the end of my Friday ramblings...or not.

Cheers

Paul

That's a question I posed before - Obsession spec <1/4 wave PV, 0.9 Strehl ... Vs what we often hear quoted for SW (<1/4 PV) and say OO offering up to 1/10 PV. Are OMI/Galaxy mirrors somehow inferior, or is there simply a lack of a meaningful standardised way of measuring/reporting mirror specs (wavelength for one) - and these parameters are not sufficient to guarantee optical quality (but may serve to highlight issues). Or is it larger mirrors possibly primarily targeted for deep sky are spec'ed accordingly? Obsession claim 'finest optics...' etc and do seem to have a very satisfied customer base indeed.

Apologies - If hopefully not going off topic too much given that it was mentioned - I'd certainly love to hear people's comments

[Scooot]

That's a question I posed before - Obsession spec <1/4 wave PV, 0.9 Strehl ... Vs what we often hear quoted for SW (<1/4 PV) and say OO offering up to 1/10 PV. Are OMI/Galaxy mirrors somehow inferior, or is there simply a lack of a meaningful standardised way of measuring/reporting mirror specs (wavelength for one) - and these parameters are not sufficient to guarantee optical quality (but may serve to highlight issues). Or is it larger mirrors possibly primarily targeted for deep sky are spec'ed accordingly? Obsession claim 'finest optics...' etc and do seem to have a very satisfied customer base indeed.

Apologies - If hopefully not going off topic too much given that it was mentioned - I'd certainly love to hear people's comments

From what I can gather, using an interferometer test to assess the whole mirror is the most important. OMI/Galaxy and OO do this and provide reports so these mirrors can be compared?

[niallk]

Yeah - what I'm kinda getting at are OMI/Galaxy like perhaps smoother Synta, and OO research grade head and shoulders above? Or is there sufficient ambiguity in test/interpretation to allow marketeering to claim really high strehl values? I personally suspect the latter but I certainly don't know (not an optical engineer!). In my engineering work I see marketeers take very rose tinted views of things on product datasheets...

Ultimately enjoyable views at the eyepiece are what counts and I guess we place trust in reputations given that we can only check post purchase...

Right apologies for straying off topic