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Posts Made By: Erik Bakker

December 23, 2007 08:58 PM Forum: Equipment Talk

Good Questar 7 vs Astro-Physics EDF130 f/6

Posted By Erik Bakker

Does anyone have some experience on the difference in visual performance between these two on the planets? I have the AP130 and want to get a used Q7 (pyrex + broadband coatings) for a step-up in visual performance.

Thanks, Erik

July 15, 2008 11:52 PM Forum: Refractors

Large Aperture Refractors for Visual

Posted By Erik Bakker

Hi Larry,

For many years I observed the planets with Leiden Obervatory's 10.5" refractor, with object glass by Alvan Graham Clark (Ø = 26.6 cm, f = 392.6 cm) on a Repsold mounting (1885).
It was capable of beautiful views, especially of Jupiter and Mars. It needed exceptional seeing to unleash it's full potential. Only once, during the great 1988 Mars opposition did I experience such seeing. At 400-600x the image stood still, revealing structures on mars not found on any map, just on the NASA/S&T Mars globe. Round, craterlike details were seen.
Interestingly, it has a Zeiss 130mm (5.1") f/18 semi apo of the early 20th century installed as a finder/guidescope. On most normal nights, that scope gave a cleaner, purer, sharper image than the 10.5". But boy, under the right conditions, the 10.5" just leaves you with images right out of the window of a spaceship.


September 3, 2008 01:49 PM Forum: Refractors

small APO refractor.

Posted By Erik Bakker

Hi Paul,

I own and use my 70 mm f/8 and 55mm f/8 fluorites a lot for the purposes you describe. If I must go really small AND light, I use the 55 mm. Under all other conditions, I take the 70mm. Both are ultra-sharp and bright for their apertures and unfortunately no longer available. Depending on the amount of money you wish to spend, I think both the TV 76 and TV 85 are good candidates. You might consider the Lomo 80/600 triplet apo from Teton telescopes with the CNC tube. Please keep the optics around f/7 to f/8. It will do the visual image quality quite a bit of good.

Kind regards,


September 23, 2008 02:05 PM Forum: Takahashi


Posted By Erik Bakker

That's a beauty Ivan! Congrats on a wonderful scope.


October 9, 2008 10:15 PM Forum: Refractors

Re: cleaning a flourite doublet

Posted By Erik Bakker

Paul Leuba said:

Give Texas Nautical a call and ask to Fred Garcia. Texas Nautical, AKA Takahashi America is the importer for all things Takahashi into the USA. Fred is the in-house optical technician. He has loads of experience with Fluorite doublets.

The C102F is very close in design to the FS102 with two exceptions, the mating elements are different and on the FS102, the Fluorite lens is coated and in front.

Hi Paul,

Just got in from another great night with the Celestron 102 fluorite. Might I ad a third exception? Slightly superior optics.

Clear skies,


May 20, 2009 07:11 PM Forum: Astro-Physics

305F3.8 Honders first image

Posted By Erik Bakker

Hi Roland,

Beautiful first light. Must be a special moment for you.

Clear skeis,


November 9, 2009 10:40 PM Forum: Maksutovs

where do we go from here?

Posted By Erik Bakker

Hi Steve,

On your quest, you're entering special territory. A 7-8" instrument is generally the optimum match for seeing conditions in most climates. Of course a 10" can do more. But you will need VERY good local seeing conditions AND a thermally stable telescope. Perhaps the most determinig factor is the actual execution of the specific sample of a scopedesign you have laid your eyes on. In order to achieve the ultimate in crispness and stability, the optics must exceed 1/12 P-V at the final imageplane = your eye, better if possible. Now that will put you on a very serious quest. As soon as you find ANY sample with that quality of any of the scopes you listed with a closed tube design, just buy it. Very few will ever come up for sale. For these samples have something very special to offer: unapproachable imagequality. In my life as an amateur astronomer for 35 years I have seen only 3 such instruments. One I was fortunate enough to buy. Observing with it is always a pleasure. The task of focussing the starlight becomes pure joy. And the objects observed are shown with unmatched tranquility and crispness. It has less to do with brand A over brand B or design C over design D. As long as the OTA has a thermally sound design, it is all about the perfection of the optics in a specific sample. Once you have found such a specimen, your quest will be over and you will keep and enjoy that instrument for the rest of your life.
Mine happens to be a Questar 7. As a bonus, it is beautiful to look at and made with unbelievable attention to detail. I have had the Zeiss and Astrro-Physics APO's up to 130mm and then some. Very nice instruments. They are all gone, no regrets.

So good luck with your quest. Hold on to your Meade Mak until you encounter a scope that just takes you to the next level.

Clear skies,


November 11, 2011 10:24 PM Forum: Refractors

Zeiss 200mm semi-apo refractor 2500mm FL on AM

Posted By Erik Bakker

Hi Patrick,

These tend to have some resemblence to a color TV, although with smooth and good optics :-)

The smaller ones are much better, especially the 110mm AS, the 130 AS is around the limit of the design. If you like Zeiss, an AS200 would be OK of course.