SingAstro

Special relativity is very easy to understand. You can either pick up a book dedicated to that, or any first year physics textbook.
It is only through the equations that you can appreciate the ideas behind the theory.

Do anyone have any opinion on celestron RASA astrograph?
How will it perform in singapore?
What mount is good for it?

tia

2D elevation contour images were obtained from NASA's MOLA, then a custom code was written to generate the 3D CAD models.


Acheron Fossae, looking from west.


Acheron Fossae, looking from east.

It's M106 in Ursa Major.
Was using the Orion G3 monochrome camera.

Thank you everyone. Finally got my kit together.
Managed to purchase a second hand William Optics Megrez 80 and a Vixen Sphinx SXW for $1.2k
Did a test shot and am very happy to get lots of galaxies at first try.

I am considering the Sky 90, FSQ 85 or the William Optics GTF81.
The Sky 90 and WO GTF81 are priced way lower than the FSQ 85. Is the extra cost for the FSQ 85 worth it?

It doesn't matter. All of them should be able to reach focus. The only thing you should care about is the distance for the reducer/flattener to the camera, which should be correct if you are using the tak camera adapters. In the case of the FSQ 85ED when reducer is used, the back focus listed is 82...

Thank you everyone for the kind advice.

Can anyone tell me the difference between metal back distance and back focus distance?
At first I thought they mean the same, but Takahashi quotes different figures for both, so I am not sure what to make of it.

Beautiful shots! What scope/mount does he use?

The image circle is 45mm. This is much smaller than APS-C. Do I still need flats?