Imaging with the 130pds

[richyrich_one]

1 hour ago, al-alami said:

Hi All.  

I've got sort of an issue, I think with the focuser. In theory I have the correct spacing between the Baader CC and my QHY 163M (with a manual filter wheel in between). It looks like I have some tilt.  I tried aligning the focuser and it seems to be okay, well at least without the imaging train attached.  Is there any way for me to work on the tilt with the camera attached during the day?  It is kind of frustrating at the moment.  I've included an image which I shot yesterday.  To be honest the image was just shot to see the stars and not for anything else, it was also shot from my light polluted roof. 

Any help would be much appreciated.

Fakhri

 

Not sure how accurate this will be using a single jpg but this is what CCD Inspector chucks out.

Do you have any visible movement if you apply some wieight to the focuser? Something I'm having to deal with at the moment. Not tackled it yet but hoping it can be adjusted out.

 

[al-alami]

5 minutes ago, richyrich_one said:

Not sure how accurate this will be using a single jpg but this is what CCD Inspector chucks out.

Do you have any visible movement if you apply some wieight to the focuser? Something I'm having to deal with at the moment. Not tackled it yet but hoping it can be adjusted out.

 

oh cool , now that's interesting ... ccd inspector, am not familiar with that .. looks like my spacing is still off

 

Edited September 18, 2017 by al-alami

[Susaron]

3 hours ago, al-alami said:

Hi All.  

I've got sort of an issue, I think with the focuser. In theory I have the correct spacing between the Baader CC and my QHY 163M (with a manual filter wheel in between). It looks like I have some tilt.  I tried aligning the focuser and it seems to be okay, well at least without the imaging train attached.  Is there any way for me to work on the tilt with the camera attached during the day?  It is kind of frustrating at the moment.  I've included an image which I shot yesterday.  To be honest the image was just shot to see the stars and not for anything else, it was also shot from my light polluted roof. 

Any help would be much appreciated.

Fakhri

 

This is one of the reasons why I changed the original focuser with a Moonlite one, I have no tilt at all with the QHY168 (just for the record, I measured its weight along with the MPCC and it is around 1150 grams).

Regards

[alacant]

2 hours ago, al-alami said:

Can it help with measuring the tilt?

Hi. Yes. You're too close top right and too far away bottom left. Choose a corner, place the star there and get it round using the tilt adjusters. If you get one corner right, the other should fall correctly too. But be warned; it's difficult to put the camera into the 130pds focuser square. The situation is marginally improved by drilling and tapping for a third thumb screw to compliment the two already present. HTH.

[rotatux]

23 hours ago, al-alami said:

I've got sort of an issue, I think with the focuser

You don't tell about capture conditions, so as I wild guess, your star elongation looks approx. perpendicular to the direction of image center. To me this looks more like field rotation, maybe mixed with a bit of coma in angles.

About tilt checking during the day with the cam train on, just a rough idea: maybe focus on a the vertical face of a far building, and check focus along a vertical line on live view ?

[Susaron]

A ghost moon taken last week while rising with the SW130PDS

 

[tony8690]

You all have some amazing pictures here!

Would you say there is much difference between the 130PDS and the 150PDS mounted on an EQ5??

Thanks,

T

 

[John78]

25 minutes ago, tony8690 said:

You all have some amazing pictures here!

Would you say there is much difference between the 130PDS and the 150PDS mounted on an EQ5??

Thanks,

T

 

A 130PDS is much more reasonable on a EQ5 with respect to payload when you've added all the cameras etc... - its diddy.

[tony8690]

Just now, John78 said:

A 130PDS is much more reasonable on a EQ5 with respect to payload when you've added all the cameras etc... - its diddy.

Is there much difference in what you can capture in photos? quality wise? will there be DSO i can capture on a 150 and not on a 130?

Thanks,

T

 

[Susaron]

22 minutes ago, tony8690 said:

Is there much difference in what you can capture in photos? quality wise? will there be DSO i can capture on a 150 and not on a 130?

Thanks,

T

 

With the 130PDS you have a wider FOV closer to the one an ED80 provides. The shorter focal length of the 130 vs the 150 makes guiding a little bit easier, moreover it is lighter.

On the other hand the amount of light being captured by the 130 is smaller, but that can be counteracted by longer time exposures.

Anyhow a friend of mine has a SW150PDS on a NEQ5 and he is very happy with it.

[Galen Gilmore]

42 minutes ago, tony8690 said:

Is there much difference in what you can capture in photos? quality wise? will there be DSO i can capture on a 150 and not on a 130?

Thanks,

T

 

The 130 has a wider field of view which makes it easier to guide and image bigger objects. But the 150 with a longer f/l is better suited to planetaries and small galaxies than the 130.

[Adam J]

 

57 minutes ago, tony8690 said:

Is there much difference in what you can capture in photos? quality wise? will there be DSO i can capture on a 150 and not on a 130?

Thanks,

T

 

To be honest the difference between the 130PDS and the 150PDS is one of the smallest jumps in the range with the focal length going from 650mm to a massive (sarcastic) 750mm so in essence there is hardly any difference between the two scopes in terms of focal length and light grasp but 750mm is competitively frustrating in terms of the number of objects that you cant quite frame nicely but that can just fit into the FOV of the 130PDS and then there is the weight difference which if far bigger than you might think for only 1 additional inch of aperture. Yes smaller galaxies will be slightly better but really not that much better.....

Get the 130PDS there is a reason there is a 67 page thread dedicated to it and nothing by comparison with the 150PDS. 

Edited September 21, 2017 by Adam J

[Adam J]

On 18/09/2017 at 13:12, al-alami said:

Hi All.  

I've got sort of an issue, I think with the focuser. In theory I have the correct spacing between the Baader CC and my QHY 163M (with a manual filter wheel in between). It looks like I have some tilt.  I tried aligning the focuser and it seems to be okay, well at least without the imaging train attached.  Is there any way for me to work on the tilt with the camera attached during the day?  It is kind of frustrating at the moment.  I've included an image which I shot yesterday.  To be honest the image was just shot to see the stars and not for anything else, it was also shot from my light polluted roof. 

Any help would be much appreciated.

Fakhri

 

I don't think that the spacing is correct from the shape of the stars I would guess at it being too much. Are you calculating the spacing to the M48 or the T2 thread on the MPCCMk3?

[Galen Gilmore]

Hey, can somebody explain to me how the coma corrector works? (as in how to use it) Because I've seen a lot about getting correct spacing with the corrector, and that worries me. Is it as complicated as I think it is or am I getting too worked up?

Also, any tips for taking flat frames? besides all the basic stuff...

[Adam J]

33 minutes ago, Galen Gilmore said:

Hey, can somebody explain to me how the coma corrector works? (as in how to use it) Because I've seen a lot about getting correct spacing with the corrector, and that worries me. Is it as complicated as I think it is or am I getting too worked up?

Also, any tips for taking flat frames? besides all the basic stuff...

It is effectively used to cancel out the field curvature caused by the light originating from the edges and center of the parabolic primary mirror not coming to a perfect focus when you move away from the primary optical axis. It causes the stars to become elongated away from the center of the image with the effect getting worse as you move further off axis. To cancel it out and achieve a flat field with good stars across the entire image the coma corrector nudges the light incident on it in the opposite direction to the original 'error'. However, this nudge has to take place at the correct distance from the sensor or instead of cancelling out the effect it will either under correct or over correct. As such the coma corrector is designed to operate at separation from the sensor to achieve optimal correction. For a DSLR that is normally easy as with a standard T-ring fitted a Badder multi purpose coma corrector will just screw on and the spacing will be perfect. In the case of a CCD that is more tricky as the distance from the front of the camera to the actual sensor within the camera is not fixed and so people have to purchase the correct spacers to achieve the correct separation as specified by the coma corrector and that will change from one CCD to another. So basically if you have a DSLR dont worry about it and if you have a CCD just ask the shop and someone like FLO will be able to work it out for you and recommend the correct spacers.

Fakhri's problems are more to do with his lack of direct  access to a good astronomy dealership at his location. (I hope he does not mind me saying so on his behalf).

Edited September 21, 2017 by Adam J

[Galen Gilmore]

7 hours ago, Adam J said:

It is effectively used to cancel out the field curvature caused by the light originating from the edges and center of the parabolic primary mirror not coming to a perfect focus when you move away from the primary optical axis. It causes the stars to become elongated away from the center of the image with the effect getting worse as you move further off axis. To cancel it out and achieve a flat field with good stars across the entire image the coma corrector nudges the light incident on it in the opposite direction to the original 'error'. However, this nudge has to take place at the correct distance from the sensor or instead of cancelling out the effect it will either under correct or over correct. As such the coma corrector is designed to operate at separation from the sensor to achieve optimal correction. For a DSLR that is normally easy as with a standard T-ring fitted a Badder multi purpose coma corrector will just screw on and the spacing will be perfect. In the case of a CCD that is more tricky as the distance from the front of the camera to the actual sensor within the camera is not fixed and so people have to purchase the correct spacers to achieve the correct separation as specified by the coma corrector and that will change from one CCD to another. So basically if you have a DSLR dont worry about it and if you have a CCD just ask the shop and someone like FLO will be able to work it out for you and recommend the correct spacers.

Fakhri's problems are more to do with his lack of direct  access to a good astronomy dealership at his location. (I hope he does not mind me saying so on his behalf).

Ah, thanks. Worry over.

[richyrich_one]

Posted in Deep Sky...

 

[Adam J]

Does anyone know the percentage central obscuration on the 130PDS?

Cheers,

Adam 

[Stub Mandrel]

Not much, I'll go and measure for you... I estimate about 10-12%

[richyrich_one]

22 minutes ago, Adam J said:

Does anyone know the percentage central obscuration on the 130PDS?

Cheers,

Adam 

Not sure how accurate this is...

 

[Stub Mandrel]

My estimate was 45mm but I wasn't going to place a rule across my secondary...

[lnlarxg]

Quick question on this thread regarding the 130pds, with a canon 550d DSLR, are there any focusing issues in achieving prime focus?

I already have a canon t-ring adaptor (baader super low profile one) and a 2" eyepiece to t-thread adapter. 

Reason I ask is having researched SGL and found lots of threads regarding prime focus with Newtonian telescopes not having enough inward (towards the scope) travel on the focuser for DSLRs to achieve prime focus.  I am certainly having this trouble with my 200p dob.

thanks 

[richyrich_one]

None whatsoever.  The P-DS scopes are designed for this.

[tony8690]

If I had a 130PDS and a eq5 with synscan would I be able to do long exposures? 300 seconds +

 

Thanks,

T

Edited September 29, 2017 by tony8690

[Stub Mandrel]

Pushing it without guiding.

I can do 120s without guiding on an EQ3 but loose a percentage of subs.

And EQ5 will be better, but I don't know if 300s will give you a decent percentage of stackable subs.