|
Star test images from Megrez .
These 5 are with out a barlow using a ToUcam.
Going from no2 outside focus focused to no6 inside focus.
Frames extracted and the best ones picked.
The conditions were quite good as seen from Andrews Newtonian and his 100mm f5 Achromate at 4/5, and there was a first 1/4 moon .
We allowed the scope to cool down inverted and no obstruction in the focuser for 1hr and Dan had the scope case open all afternoon so that the scope was not insulated.
It was initially obvious that there was some improvement from before visually .
Visually we used a Radian and orthoscopics eyepieces with and with out an Orion 3 element 2x APO barlow and a 4x Powermate
Imaging we used the 2x Barlow as well as just the imager.
Overall the central part of the star tests was steadier than before but still showed the same heat like distortions and haze masking the inner rings.
At first you would say that this is heat distortion except that on both nights it showed no improvement over the whole night. 4hours plus.
You would assume there to be some improvement over 4 hours if it was heat.
The temperate drop on both nights was not extreme and the nights were fairly mild for winter.
So the objective should have been able to come to temperature .
You can see the centre is a wash with a blue and green haze and the focused star has a blue halo surrounding it .
The focused star a tad worse than my Celestron 80Ed or Tony's Orion Ed.
My star test pics can be seen at the review section for comparison and show a very well defined ring system.
Even Andrews old F5 Achromate showed a better star test.
No mater how far in or out of focus we racked the Megrez it just would not show a well defined diffraction rings or show the central star and you can see the outer was better than the inner focus.
The last thing we did was cranked up the power on the moon to 90x per inch ---280x , and was surprised to see a fairly well defined view with little atmospheric heat distortion.
This was quite a good result .
Jupiter would not take this magnification and 112x was it's limit .
This had me thinking that may be the star test was acceptable ????
This had me thinking all the way home , so when I got home that night I pulled out the Celestron with the same power and no cool down and it was still a better image.
90x per inch is pretty dam good for a refractor thou and as Dan points out low power views are very good..
This is what i bought my ED for low power imaging and not high power planetary use.
As I have said before , mechanically the Megrez is first class but optically there is some thing amiss.
If this is a heat issue life is to short to wait for the triplet to come to temperate.
Williams did offer Dan the choice of spending even more money and buying the Florite APO.
From what I have read on the forums this appears to bve the model of choice for imaging but comes at a much higher price.
I am just hopping that some one at the Queensland Astrofest will have another Megrez triplet or another brand of triplet APO there that I can have a looky through just for a comparison as this has got me baffled.
Mark
|