Observing Landolt fields

Gianlucanigro · September 21, 2024, 7:20am

Hi,

I’d like to determine the transformation coefficients for iTelescope T72 which I’m using for taking images of V1725 Sco.

Unfortunately all the globular clusters managed by TG are now too low on the horizon** so I was planning to use the Landolt fields, but given the FOV very small and the small number of standard stars in the fields I can’t have enough stars in a single image.

I was wondering which is the best procedure to use in a case like this.

If I take images of different fields I imagine that also extinction has to be taken into considerations.

Any suggestion?

Thanks

** with the exception of NGC3252 but I get only 4/5 standard stars in the image

bskiff · September 21, 2024, 2:53pm

You might have a look at the extended data on Landolt fields and around globuar and open clusters by Peter Stetson:

…which include large numbers of stars observed on ‘many’ nights very closely tied to the Landolt system by procedures well-documented in his papers.
Yes, if yo take images of several fields, atmospheric must be taken into account in reducing the data. If the airmass range is not too large, it is reasonable to simply adopt some typical extinction coefficients.

\Brian

MZK · September 21, 2024, 3:33pm

Gianluca:

What is the FOV of T72? A few Landolt Fields do have many tens of standard stars.

Please share a few NGC3532 images with me (MZK) in VPhot.

Ken

Gianlucanigro · September 21, 2024, 5:14pm

Thanks Brian,

I’ll give a look

Gianlucanigro · September 21, 2024, 5:18pm

Hi Ken,

here you can find the details for T72 Observatory: Deep Sky Chile at Rio Hurtado Valley, Chile - MPC X07 Telescope: T72 3411 mm f/6.8 PlaneWave L-500 + FLI ML16200 Timezone: UTC -4:00 Santiago, Chile : Support

I shared a set of images of NGC 1252 on VPHOT

The scope has a full set of UBVRI filters and the image quality looks good

Probably I’ll have to wait until February/March when M67 will be visible

bkloppenborg · September 21, 2024, 6:09pm

While not Landolt fields, AAVSO has several well calibrated standard fields that we recommend people observe. They should be suitable for determining transformation coefficients.

MZK · September 21, 2024, 6:20pm

Gianluca:

NGC 1252 was selected to work with small refractors with large FOV (2 deg.). It is not useful for T72 with a FOV ~25’. Too few comps as you found.

SA98 at RA~07H would be next in line with many comps in 30’ field. A little before M67 which is slightly north (+10).

If you look at the list Brian provided link for (that you know about), it is often a compromise to get a good match at a specific LST time.

Actually, try M11 early in the evening (RA~19H)? Small field and lots of comps.

Ken

Gianlucanigro · September 22, 2024, 5:40am

Hi,

using M11 quite probably is the easiest way.

I’ll try to plan some images, unfortunately right now the T72 is offline

DEY_VAR · September 22, 2024, 1:30pm

Have a look at the AAVSO Variable Star Plotter (VSP) Standard Fields page. Nice table of all the standard fields with locations, FOVs, etc. Charts and tables for each.

https://apps.aavso.org/vsd/stdfields

Gianlucanigro · September 24, 2024, 4:49am

Hi,

M11 is definitely the right choice, Vphot identifies 415 standard stars in this V exposure (60 secs)