Reading your post again I realise you have the 102mm f/4.9 doublet with ordinary glass.
This indeed may be worse than the ED spotting scopes.
The CA is considerable, also possibly spherical aberration.
In addition fast refractors cool badly and don't perform well until 30 minutes outside.
If the temperature continues to fall they may still not be good.
I have both the 80mm and 102mm fast refractors.
They may also not be very good at high magnifications, they may just not be made to very high standards.
Perhaps stop the 102mm scope down to 80mm.
The mirror should not be a problem. I thought you had a prism.
Also I doubt that the scope is much out of collimation, but an out of focus star should show this.
I used a custom made 123mm f/5.15 Jaegers objective refractor extensively.
Although it was good for deep sky objects, using it on Saturn, intensity estimates were not very accurate.
It showed stars down to magnitude 13.1 in town.
The most used magnification was 80x, but also 16x, 30x, 100x and 145x.
At 210x it was slightly out of collimation.
It is a cemented doublet without collimation possibility.
The 120mm refractors at 250x at 3 a.m.showed the tiny minute markings on a clock tower 4.7 miles away at one arcsecond over houses and parks.
They have very high quality hand made objectives.
Of the 20 refractors from 60mm to 135mm that I recall, two were of poor quality.
Four were ED glass, 14 ordinary doublets, one 105mm f/16 Fraunhofer objective and an essentially perfect Ross 100mm f/15 triplet.
In addition a Tewe Petzval 4 element 120mm aperture f/5 photo lens was of astro quality on Saturn.
The 172mm aperture Zeiss f/7 Aero Triplet from 1920 was also of astro quality and possibly aspherised. This a Cooke photo triplet.
I also briefly used the Harvard 9.5 inch refractor, and a Cooke 6 inch refractor.
I extensively used a 135mm f/16 observatory refractor.
My friend's 60mm Royal Japanese refractor showed Tethys and Dione.
To repeat, I am not surprised by the poor performance of the 102mm short focus refractor.
However, there are Baader fringe killer filters of different types and also a semi apo Baader filter that may help a lot, assuming that the objective is well made, which may not be the case.
We have had lying snow for a week and minus 7C or 20F.
Unusual for us.
Regards,
B.
This indeed may be worse than the ED spotting scopes.
The CA is considerable, also possibly spherical aberration.
In addition fast refractors cool badly and don't perform well until 30 minutes outside.
If the temperature continues to fall they may still not be good.
I have both the 80mm and 102mm fast refractors.
They may also not be very good at high magnifications, they may just not be made to very high standards.
Perhaps stop the 102mm scope down to 80mm.
The mirror should not be a problem. I thought you had a prism.
Also I doubt that the scope is much out of collimation, but an out of focus star should show this.
I used a custom made 123mm f/5.15 Jaegers objective refractor extensively.
Although it was good for deep sky objects, using it on Saturn, intensity estimates were not very accurate.
It showed stars down to magnitude 13.1 in town.
The most used magnification was 80x, but also 16x, 30x, 100x and 145x.
At 210x it was slightly out of collimation.
It is a cemented doublet without collimation possibility.
The 120mm refractors at 250x at 3 a.m.showed the tiny minute markings on a clock tower 4.7 miles away at one arcsecond over houses and parks.
They have very high quality hand made objectives.
Of the 20 refractors from 60mm to 135mm that I recall, two were of poor quality.
Four were ED glass, 14 ordinary doublets, one 105mm f/16 Fraunhofer objective and an essentially perfect Ross 100mm f/15 triplet.
In addition a Tewe Petzval 4 element 120mm aperture f/5 photo lens was of astro quality on Saturn.
The 172mm aperture Zeiss f/7 Aero Triplet from 1920 was also of astro quality and possibly aspherised. This a Cooke photo triplet.
I also briefly used the Harvard 9.5 inch refractor, and a Cooke 6 inch refractor.
I extensively used a 135mm f/16 observatory refractor.
My friend's 60mm Royal Japanese refractor showed Tethys and Dione.
To repeat, I am not surprised by the poor performance of the 102mm short focus refractor.
However, there are Baader fringe killer filters of different types and also a semi apo Baader filter that may help a lot, assuming that the objective is well made, which may not be the case.
We have had lying snow for a week and minus 7C or 20F.
Unusual for us.
Regards,
B.
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