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A few first results with an ALPY200

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#1 mborland


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Posted 03 March 2024 - 08:38 PM

I purchased an ALPY200 switch module following the seminar in early February. Thanks to lots of clouds, I'm just getting some first results.


As with my ALPY600, I'm using a 120-mm APO refractor and ASI533MM science camera. The guiding and calibration modules are there as before.


I first tried an 6.5 magnitude A0V star, namely, HD89239. This allowed figuring out how to do the wavelength calibration, since I didn't use the calibration module. I got an rms deviation of about 0.7 Angstrom with a second-order fit using four Balmer lines.


Next, I went to HD97633, which is the reference star I wanted to use for my two science targets. After calibration and response correction, I compared to the MILES spectrum, which demonstrates decent agreement. I think the region below 4000 A is a bit suspect.HD97633.jpg


My first interesting target was SN2024gy, for which I took 4x720s exposure with gain of 400. I was surprised at how dim this SN looked on the guiding image compared to my observations in January and February. The spectrum after calibration and response correction agrees well with the SNID templates for a Type Ia supernova.


SNID indicates an age of 30 days, which is not right (more like 90 days).


With the ALPY600,  I was using typically 20x720s exposures with gain of 400, and the SN looked much brighter then. So it seems I got a significant improvement, e.g., a factor of about 5.


My second science target was NGC3147, an active galaxy with a red shift of 0.0094. I tried this one because it's one I struggled with using the ALPY600.


(The spectrum drops below 4500 A, which could be a response correction problem as indicated above.) I can roughly estimate the redshift from the (apparent) Halpha emission line as 0.008, which is about right. Compared to the ALPY600 results, I got a decent spectrum in 7x720s compared to an arguably better result in 26x720s:


(Note that my ALPY600 result for NGC3147 does not have a response correction.)


So far, I'd say the ALPY200 is working well and allows getting results with less exposure time. It's hard to put a numerical factor on it, but if I had to I'd say a factor of 3-5.



Edited by mborland, 03 March 2024 - 08:53 PM.

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#2 robin_astro



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Posted 04 March 2024 - 11:24 AM

The continuum shape of NGC3147 looks roughly  right compared for example with this spectrum


from NED


though perhaps drops off more severely below ~4000A





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