Archive for category Do it yourself
My recent scope acquisition: an Orion Maksutov Newton 190mm… I bought a “bundle” (brand new Atlas mount and showroom Mak Newt) in July 2009 .
I would recommend anybody buying a telescope to make this investment (artificial star and the book) and go through this procedure. It is worth it. A couple of month ago, I had to return a first Maksutov-Cassegrain because of some optical issues that was somewhat revealed looking a stars (but was not sure if it was due to turbulence or not) and the defect was revealed very clearly with the artificial star testing. I got a new scope because I was in the 30 days return policy – and the new scope was as good as the Mak-Cassegrain optical design permits…
Waiting for a great seeing to do a “real” star testing may not happen during the 30 days return policy. Make sure that when you do artificial star testing you have plenty of space – otherwise you introduce aberration that would not happen with “real” stars. In my case I placed the artificial star at least at 200 yards from the telescope.
To come back to my new Maksutov-Newton – I made the test and found (after thorough collimation) the optics extremely satisfactory, with nice diffraction patters in focus, and very similar (almost textbook-like) forward and inward out of focus diffraction patterns. Visual image of Jupiter was also crisp and contrasty, making it a good planetary instrument when well collimated, even though this is not the primary purpose of this scope (which is flat field astrophotography).
Look at the Perseus double cluster picture taken with the Mak Newton. Stars are pinpoint even at the edge of the picture (Canon EOS full frame). You would not have the same picture with a Newtonian (except if using a coma corrector) or even a regular Schmidt Cassegrain telescope.
This shot of M13 was taken with the Mak-Newt and my Qhy9 Black and White camera.
This shot of NGC 981 on this page was taken using the Mak Newton with my Canon XTi and an Orion Skyglow filter.
I tried different techniques to bring in focus my Canon XTi,
Even by taken series of short exposures and using the preview / zoom functionality of the DSLR camera I found issues and results were not completely satisfactory.
I found mention of the Bahtinov mask on different blog post – and decided to give it a try.
The Bahtinov mask was built in-house for my orion 102ED using Bahtinov’s mask free templates posted on this web site
The materials used for building the mask can be found in stores such as Office depot,
I used a black plastic portfolio. Use a portfolio not too thick, that can be easily cut using a paper cutter – but rigid enough to be used as a mask. Using adhesive, the template (printed from my computer on Letter format) was glued on the portfolio plastic sheet. I used a DVD plastic box as a cover to secure the mask on the 102ED optical tube.
The way to bring the camera in focus is simple. The basic principle is the same as without the mask – doing an approximate in-focus first using the view finder – then tweak the in-focus by using short exposure and the preview mode of the camera – with the Bahtinov mask in front of the optical tube.
Below are pictures from Betelgeuse. The left picture is a 3 sec. exposure and shows Betelgeuse out of focus. The right picture is in focus. When in focus, the diffraction spikes are symmetrical with a easy to recognize pattern.
Betelgeuse – 3 sec. exposure – out of focus (left) and in focus (right)
Here are some pictures taken using the mask for focusing. The picture was shot in San Bruno, CA in a very light polluted sky – using the Orion SkyGlow anti-pollution filter and a Canon Digital Rebel XTi DSR Camera. Focus on M1 was made using approximately 6 shots on 3 sec. each on Betelgeuse. In this astrophoto session on 3/27, Focus was not changed during 2h where a total of 5 deep sky objects were shot using multiple short time exposures.
Picture of M1 – 3/27/2009
I had for some time the Orion 102ED premium refractor – and I was not able to find any ready made solar filter in the market to fit this scope including at the Orion’s stores.
I finally decided to buy a Baader solar filter film to build a solar filter. I ordered the baader solar filter film (A4 size) at the scope city web site.
I followed the instruction posted on the Baader planetarium web site. I was very pleased with the result – the visual observation exceeds whatever I saw with glass filters on same or larger scopes and this for one fourth of the price I paid for glass filters!! . I had also extra film left to build filters for my guide scope and finder scope.
I bought the Visual solar film (it comes in two flavors – for visual observation and for Astrophotography). But I was able to use the visual solar film for both visual observation and astrophotography. I’ll post solar pictures I made with this setup very soon.
Here is a picture of the whole setup – the 102ED premium refractor and home made solar filter with the Baader solar film …