Errors with SeeStar S50

Science Smart Telescope Photometry
1

I have been submitting data using my S50, and have wondered about the MERR in the report. I typically see an error with transformation of anywhere between 0.001 to 0.04 depending. I have redone my transformation coefficients with much more data and I have seen the MERR decrease markedly so I am seeing on the order of 0.004 or less across all filters V, B, and R I do not have a good feel for these numbers. Are they good or bad? How can I improve my data?

Thanks

Scott

2

What does your MERR value represent? Standard error of the mean? Standard deviation? If either of these, calculated from how many observations? Measured mag minus catalogue mag (for a check star)? If 0.004 or less applies to any of these you should in my opinion be happy with the result.

3

Greetings. I moved this post over to the Smart Telescope Photometry thread in hopes that it gets greater interest.

4

Hi Roy:

Actually, I am not sure. I will contact Han and find out. This is the value that is reported in my submitted text file. It is reported for each submitted observation, which in my case is typically a stacked fit of 15 or more 20 sec exposures.

Scott

5

Hi Roy:

I talked with Han, the author of ASTAP, and he indicated “The MERR of the Var is simple the standard deviation of the check star. Only when the value 2/SNR of the Var is larger than this last value it is taken. So, it will not include systematic errors in the calculation like your mentioned measured magnitude minus the catalog magnitude for a check star.”

We talked for a bit regarding this, and he will look into the citing the different types of errors, like measured magnitude minus catalogue for a check star.

Scott

6

Hi Scott,

Thanks. I don’t understand:

(Edit) I don’t know why the MERR for the Var should be the SD of the Check. Why not just SD of the Var? Perhaps the sentence I didn’t understand relates to the reason?