7 replies to this topic

[bluesilver]

Hi,  I currently have the older version of ASTAP and i am currently using it in the program Astro Photography Tool ( APT )

I currently have the old data base witch is either H17 of H18,  I just can't remember which one,  I think i went with the largest one.

 

I was just looking at ASTAP sits at the new version and how to do the install.

 

I am just a tad confused now on which databases i am suppose to be looking at here.

The site tells me:

You will need only one database. Is your field of view 0.6 degree or larger you can download either the d05 or d20 or D50. The d05 is the smallest. The d50 is the largest. Using the d50 has no drawaback accept it is larger, about one gbyte and a little slow. The V17 is only required for photometry of wide field of view. The H17,  H18, G17, G18 can be uninstalled/deleted.

 

So looking at astronomy.tools site to find my field of view i get:

Field of view = 1.28° x 0.86°  Dawes limit = 0.77 arc/sec  Resolution = 0.74 x0.74 pixel

 

Another scope i am looking at brings the number slightly lower to:

Field of view = 1.12° x 0.75  Dawes Limit = 0.46 arc/sec  Resolution = 0.65 x 0.65 pixel

 

So,  I am not sure if i should just be looking at going with the larger D50 option or looking at the D20 option,  I think the D05 might be right on the limit possibly?

 

Next,  do i even need the V17 , W08 , Hyerleda ?

 

I am only using ASTAP for plate solving in APT ( Astro Photography Tool )

 

Any advice would be appreciated.

 

 

[speedster]

The smaller files have fewer stars.  With a narrow FOV less than 0.6, you may not have many stars in the field to solve and you may need the bigger file which includes dimmer stars.  Imagine a situation where the data base goes down to mag 5 stars but you have a very narrow FOV and it has one mag 5 star and the rest of the stars are dimmer.  You are trying to solve with a database that only sees one star in your FOV.  With the bigger file, I don't know what "a little slow" means in terms of seconds but I run the big H18 files and don't notice an unusual wait but I've never compared the it to other files.

[bluesilver]

Appreciate the reply and advise.

I am now thinking is it even worth the trouble to download the latest versions.

I have now found that i have the larger H18 data base installed.

It has been working fine.

Maybe i am better of just staying with what i have already got.

[ButterFly]

The simple way is to install the smaller one, then plate solve far from the Milky Way.  It it can, you should be fine.  If not, go for the larger one.

 

But yeah, if it aint broke ... .

[han.k]

The new D05 should work fine for you.  But you could also install the new D20 or D50. There is no penalty for installing the D50 except for the larger size and maybe a little slower. But these databases are all smaller then the H18. You could also stay with the H18. With your field-of-view there will be no notable performance difference. The H18 will be supported for some time.

 

The new databases are sorted on star density and not on magnitude. These databases are constructed to have a constant star density per square degrees sky. For navigation (solving) there is no need to fill the database with numerous stars when there are sufficient brighter stars available. But in sky areas where there not many stars the new database goes deeper then the older H18. It goes down to magnitude 21 if required.

 

D50 stand for a database with a star density up to 5000 stars per square degree. Size is about 873 mbytes.

D20 stand for a database with a star density up to 2000 stars per square degree. Size is about 400 mbytes.

D05 stand for a database with a star density up to 500 stars per square degree.Size is about 102 mbytes.

 

The new D50 will be beneficial for setups with a small field-of-view. So when your image with a focal length of maybe 2 meters or a field-of-view of 0.3 or 0.2 degrees. The databases are just released so any feedback is appreciated. Especially if your working at the field-of-view limit of the database. These limits are not hard. Outside the limit the reliability goes down.

 

The V17 database will also be replaced in the next days. There will be one new database for the field-of-view range between 10 and 20 degrees and a Johnson-V magnitude version of the D50 for photometry I will call V50. Normally the databases contain the Gaia Bp (blue) magnitude which covers roughly the visual spectrum.  For photometry is is better to have the calculated Johnson-V magnitude.

 

For creating each of these databases my computer has to work a few days. You could argue are the D05 and D20 really required and can't you use the D50 for all applications?. But a small size database could be handy. As an experiment I have also created a D80 but I don't think there are setups imaging consistently with a field-of-view of something like 0.1x0.1 degree.

 

Han

[johnpd]

SharpCap does not recognize the new "D" database versions.

 

JohnD

[bluesilver]

Appreciate all the replies and advice.

I might just stay with what i have then for now as it is working just fine.

I don't use SharpCap for plate solving or finding targets yet,  but might be later on,  so good to know SharpCap doesn't work with the new version yet.

[johnpd]

My error. Apparently you had to install the latest .EXE along with the new databases. It then works.

 

JohnD