Telescope Reviews: PEC - This can't be right! NEQ6

· Get a Cloudy Nights T-Shirt

· Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu… uh, User

You are not logged in. [Login]

Entrance · Main Index · Search · New user · Who's Online
FAQ · Calendar

Equipment Discussions >> Mounts

Pages: 1

nobbygon
super member

Reged: 03/20/09

Loc: Australia

PEC - This can't be right! NEQ6
#5568172 - 12/12/12 07:41 PM Attachment (53 downloads)

Hi,

I've recently pier mounted my NEQ6 and last night finished my polar alignment so that the star wouldn't move over 10 mins. I've never tried PEC before so decided to give it a go. My results are attached. I captured the data on a DSI II Pro and an Orion short tube 80 (FL 400mm)using PHD. Shot on a star on the meridian near the equator.

I can’t believe that my PE is only +9 -12 arcsecs. I was expecting more like +- 30. What could I have done to get incorrect data that would show a PE less than what it really is? Could it be that the scope that I shot the data through has a focal length that is too short?

I wanted to see how my guiding was going and to my surprise I've never seen it as good as this before. OSC index of 0.19 and RMS of 0.12. I've never seen numbers that good before. Maybe it’s down to a really accurate polar alignment. Any thought here?

Cheers for any help,
Angus.

Post Extras:

nobbygon
super member

Reged: 03/20/09

Loc: Australia

Re: PEC - This can't be right! NEQ6 new

[Re: nobbygon]
#5568174 - 12/12/12 07:42 PM Attachment (41 downloads)

And the guiding graph

Post Extras:

orlyandico
Carpal Tunnel

Reged: 08/10/09

Loc: Singapore

Re: PEC - This can't be right! NEQ6 new

[Re: nobbygon]
#5568328 - 12/12/12 09:35 PM

+10 / -12 is a very good figure. It is possible to get an NEQ6 with that level of precision.

The only reasons I can see for mis-reporting of this figure is (1) not factoring in the declination when importing the PHD log into PECPrep; (2) incorrect pixel size when importing the PHD log; for example the Meade DSI has 9.6 x 7.5 um pixels. If the wrong axis gets chosen when calculating, your PE would be proportionately larger or smaller; and (3) incorrect focal length of the guide scope.

However, given your data (400mm FL and DSI Pro II) that's an image scale of 4.27" per pixel. RMS of 0.12 means you are guiding at (4.27 * 0.12) = 0.51" ! that is an amazing figure, comparable to a Mach1.

The best I can do on my CGEM is 0.18 RMS @ 9.71" / pixel which is 1.75" RMS. This is about 3X your figure. But then again my CGEM has +/- 20" of PE.

Post Extras:

korborh
professor emeritus

Reged: 01/29/11

Re: PEC - This can't be right! NEQ6 new

[Re: orlyandico]
#5568342 - 12/12/12 09:42 PM

Is that star saturated?

Post Extras:

andysea
professor emeritus

Reged: 09/03/10

Loc: Seattle, WA

Re: PEC - This can't be right! NEQ6 new

[Re: orlyandico]
#5568423 - 12/12/12 10:59 PM

Yeah that's about right. I get 0.3"~0.5" RMS with my mounts.
I think it means that the PE is easily guided out right? That NEQ6 is a keeper!

Andy

Edited by andysea (12/13/12 01:27 AM)

Post Extras:

nobbygon
super member

Reged: 03/20/09

Loc: Australia

Re: PEC - This can't be right! NEQ6 new

[Re: andysea]
#5568439 - 12/12/12 11:12 PM

Yeah I'm prety sure the star is saturated. If not it's pretty close. Does that have anyhting to do with how PHD guides?

Post Extras:

korborh
professor emeritus

Reged: 01/29/11

Re: PEC - This can't be right! NEQ6 new

[Re: nobbygon]
#5568566 - 12/13/12 01:22 AM

If star is saturated, the centroid calculated by PHD would be incorrect and hence show its not moving. All those saturated pixels and large size of the star can mask the movement of the centroid as information is lost.

Post Extras:

gezak22
professor emeritus

Reged: 08/15/04

Loc: Goleta, CA, USA

Re: PEC - This can't be right! NEQ6 new

[Re: nobbygon]
#5568579 - 12/13/12 01:42 AM

Quote:

Yeah I'm prety sure the star is saturated. If not it's pretty close. Does that have anyhting to do with how PHD guides?

Under 'Tools' there is an option 'Auto select Star' or something like it. It automatically selects the star with the highest SNR in the guide image.

Post Extras:

andysea
professor emeritus

Reged: 09/03/10

Loc: Seattle, WA

Re: PEC - This can't be right! NEQ6 new

[Re: gezak22]
#5568763 - 12/13/12 07:32 AM

Quote:

Quote:

Yeah I'm prety sure the star is saturated. If not it's pretty close. Does that have anyhting to do with how PHD guides?

Under 'Tools' there is an option 'Auto select Star' or something like it. It automatically selects the star with the highest SNR in the guide image.

Does that really work? I'm always afraid that PHD will pick a hot pixel by mistake. I have to say I never tried that option tho.

Andy

Post Extras:

EFT
Vendor - Deep Space Products

Reged: 05/07/07

Loc: Phoenix, AZ

Re: PEC - This can't be right! NEQ6 new

[Re: nobbygon]
#5568957 - 12/13/12 10:30 AM

A mount with +/-30 would actually be a pretty bad example. Your results are on the better side of average which I would consider to be somewhere in the +/-15 to 20 range. Pier mounting and good alignment have not hurt you either.

Post Extras:

gezak22
professor emeritus

Reged: 08/15/04

Loc: Goleta, CA, USA

Re: PEC - This can't be right! NEQ6 new

[Re: andysea]
#5569031 - 12/13/12 11:10 AM

Quote:

Quote:

Quote:

Yeah I'm prety sure the star is saturated. If not it's pretty close. Does that have anyhting to do with how PHD guides?

Under 'Tools' there is an option 'Auto select Star' or something like it. It automatically selects the star with the highest SNR in the guide image.

Does that really work? I'm always afraid that PHD will pick a hot pixel by mistake. I have to say I never tried that option tho.

Andy

You bet it works. The reason why it will NEVER select a hot pixel is because PHD knows what hot pixels look like (isolated pixels) while stars have gaussian pixel distributions. PHD is pretty clever.

Post Extras:

andysea
professor emeritus

Reged: 09/03/10

Loc: Seattle, WA

Re: PEC - This can't be right! NEQ6 new