Forum Replies Created
It looks like Gemini are updating the website with new grating transmission measurements:
There are still a lot of them TBD but the B600 throughput for the South is there, measured in 2015. Hopefully the north will also come soon!
That’s an excellent question! As you know I have a survey program using the B600 as well, and so I would also be very interested to know the answer to this.
By convolving the grating transmission, detector response and stellar blackbody I get something that is different from what I observe in the data, so perhaps the grating transmission information does need to be updated.
If you don’t get a response in a week, I would say to email the Helpdesk if you haven’t already: https://www.gemini.edu/sciops/helpdesk/submit-general-helpdesk-requestFebruary 8, 2017 at 4:31 pm in reply to: What is your Technique to Correct for Instrument Response in your Flat-Field? #1490
Oops – yes I absolutely meant divide as well, not subtract. I must have mis-typed!
Thanks for the suggestion for cross-dispersed data. My data aren’t cross-dispersed, but it’s useful to have ideas for this procedure. I’m trying to stimulate discussion on this forum about best practices for data reduction, so it’s really helpful to have your input.
Thanks!February 7, 2017 at 5:19 pm in reply to: F2 imaging reduction: Imcoadd – no good objects in common #1487
I don’t use FLAMINGOS-2 myself, but I wanted to point you in the direction of the Gemini Helpdesk if you haven’t seen it already. They should be able to help with problems like this, as yours is quite a specific problem that may not be able to be answered on here. If you scroll down under the “topic” dropdown, you can select “Gemini IRAF”.
Here is a link to the Helpdesk:
Thanks, and I hope you can resolve the problem soon!
@sebaguro: At the bottom of the page given above is also an R400 spectrum which has the same lines in it that you get with the R150. I have used that plot to wavelength calibrate R150 data.
Thanks for the quick reply! Sorry I should have mentioned – we did already flip the x-axis, so I know that isn’t the problem. The spectrum in the plots is similar to the data but not quite right. Sorry I can’t post an example – I was asking on behalf of someone else and I don’t have their data. I’ll get in touch with her and try to post an example, or see if she can post it.
In my case, I have data taken in 2012 which match well but her data was taken this year, so I can only assume that there may have been some subtle changes since then.November 30, 2016 at 4:50 pm in reply to: GNIRS reduction – Standard star subtraction and telluric lines #1441
Thanks for the advice – that’s very helpful!November 19, 2016 at 4:33 am in reply to: GNIRS reduction – Standard star subtraction and telluric lines #1438
That’s a great question and I would also be interested in hearing answers and thoughts on this. I am an optical observer myself but I do have some infrared spectra that I have not yet reduced.September 20, 2016 at 9:50 pm in reply to: Discussion Topic: Correcting for Slit Tilt in GMOS Spectra #1375
Yes, that makes sense – our slits are only short. Thanks for the reply.September 14, 2016 at 9:02 pm in reply to: Discussion Topic: Correcting for Slit Tilt in GMOS Spectra #1367
@jgagne: Thanks for sharing your code! This does look similar to what I did although with a lot more options. I’m curious – in what circumstance would you use the option to smooth? I can see how it would reduce noise but would it also reduce the significance of the cross-correlation peak?
September 14, 2016 at 9:01 pm in reply to: Discussion Topic: Correcting for Slit Tilt in GMOS Spectra #1366
- This reply was modified 3 years ago by Catherine Huitson.
@jturner: Thanks for the reply. Yes, that’s true that is is taken out in the reduction. I was mostly asking to stimulate discussion about people’s practices, or for people who may be doing their own reductions.
So far I’ve found that the differences between rows in the arcs were linear in my data but then the effect was very small overall (< 1 pixel shift over all ~200 rows) and so my experience probably isn’t representative. I haven’t experimented with higher-order functions but I would be interested to see at what level of tilt the effects become non-linear.
I agree with using arcs for tilt and science spectra for correcting zeropoint shift – this is what I do as well.