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Imaging with the 130pds


Russe

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1 hour ago, Stub Mandrel said:

Do you have the 0.9x Skywatcher CC ahnd an APS-C

Hi. The latter yes. The cc, not sure. It's an unbranded Chinese affair. It plate solves to less than the quoted focal length, but exactly how much... Anyway, thanks for the framing hint, and yes, I can get the whole of the curve of the chain with room to spare. On snap 10 as I write....

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First light: Markarian's Chain. Having got used to 208mm f3.9, the first thing that strikes you is how much longer you need to get anywhere near... but hey, just look at that FOV...

Stuff that is gonna need fixing: the focuser, the springs on the primary, the secondary allen key adjusters, the flimsy dovetail, the tube... The latter is a bit of a flashback to those awful blue skywatchers from the 90's; breathe too heavily and it /bent/flexed/dented and went out of collimation. I thought that by now they'd have done something about that. Aluminium perhaps? At least something that doesn't make that awful tinny sound when you drop the allen key down the tube.

But these are minor quibbles. For what it cost, it's amazing. I'm gonna read through the whole thread and see if I can pick up any hints.

Any comments/hints/tips most gratefully received. Clear skies and thanks for looking.

markarian.jpg

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1 hour ago, alacant said:

First light: Markarian's Chain. Having got used to 208mm f3.9, the first thing that strikes you is how much longer you need to get anywhere near... but hey, just look at that FOV...

Glad you got the 130pds, welcome to the club :)

Are you using a cc? I'm waiting for my spacers to arrive so i can use mine.

 Very nice first light for the 130pds. Congrats

 

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1 hour ago, alacant said:

First light: Markarian's Chain. Having got used to 208mm f3.9, the first thing that strikes you is how much longer you need to get anywhere near... but hey, just look at that FOV...

Stuff that is gonna need fixing: the focuser, the springs on the primary, the secondary allen key adjusters, the flimsy dovetail, the tube... The latter is a bit of a flashback to those awful blue skywatchers from the 90's; breathe too heavily and it /bent/flexed/dented and went out of collimation. I thought that by now they'd have done something about that. Aluminium perhaps? At least something that doesn't make that awful tinny sound when you drop the allen key down the tube.

But these are minor quibbles. For what it cost, it's amazing. I'm gonna read through the whole thread and see if I can pick up any hints.

Any comments/hints/tips most gratefully received. Clear skies and thanks for looking.

 

Youre right about the primary and focuser needing a little attention (moreso the focuser), but everything else is already in a passable state - except the inside would need flocking (including the drawtube), the paint they use isnt quite black enough for my taste.

The steel tube is preferable to aluminium, and its dinky size is its strength (small tubes flex less) - and the dovetail will suffice (lets face it, its not a heavy telescope!). Your starfield looks ok, so no need to go adjusting any tilt yet. Quite a few have done something  to modify theirs, usually in improving the camera mounting method - ie: drilling a third hole in the EP holder so you have three thumbscrews 120deg apart (helps prevent tilt in the imaging train).

Oh, get a dovetail bar for the top as well. That will be your guider platform, and it has the added bonus of increasing overall rigidity (also, a pretty useful handle). For info, the holes on top of the tube rings are 1/4" UNC, or if you cant get that a 1/4" Whitworth will do the job.

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2 hours ago, Uranium235 said:

get a dovetail bar for the top as well

Hi and thanks for the tips. Here's the state of play ATM. Oh, and the spring which pushes on the secondary seems too weak; unless you collimate vertically, the spring isn't strong enough to respond. Apart from the third screw, is there any cure for the focuser? It just doesn't seem capable of -or was designed to- carry a dslr.

IMG_20170520_191903.thumb.jpg.975571b828432e639bb9fe0e77773272.jpg

IMG_20170520_191828.thumb.jpg.a6c8e759f50f1ce356339f46bd010df4.jpg

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3 hours ago, Atreta said:

Are you using a cc? I'm waiting for my spacers to arrive so i can use mine.

Hi. Yes, there's a cc. Maybe try without the spacers? Unless you have the Baader, I don't think it'll matter much. HTH.

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15 minutes ago, alacant said:

It just doesn't seem capable of -or was designed to- carry a dslr.

Mine is quite content with a 450D hanging off it, never had it slip. You can tighten it up, loosen the setting grub screws on the centre line of the plate above the adjuster, tighten the corner screws to make it just a tad too tight, then tighten the two adjuster screws until it is spot on. May need a couple of tries to get it perfect, but once done it should hold a DSLR for focusing while still being very smooth, then naturally you lock it with the lock screw.

I bet a lot of people's issues with this focuser are down to poor adjustment.

BTW I reversed the focusing screw to eliminate conflict between mount and low-speed control, as with a camera on I have the focuser on the mount side.

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40 minutes ago, alacant said:

 is there any cure for the focuser? It just doesn't seem capable of -or was designed to- carry a dslr.

After a bit of tweaking the tension (so its quite stiff), mine was ok with the 383L+ and FW, which is the best part of 2kg. There are no clear instructions from SW on which hex bolts to tighten up on the focuser, but you might find this useful:

https://teleskop-austria.at/information/pdf/SWN1507eq3_Skywatcher_Crayfor-Auszug_justieren.pdf

You might need some counterweight at the primary end too, a lot of the time peoples setups are quite camera heavy. I used a strap-on leg weight for mine.

 

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8 minutes ago, Stub Mandrel said:

you lock it with the lock screw

That's the problem; tighten it and it tilts the focus tube and/or changes the focus. The only way I could keep it flat was by trial and error between adjusting the two screws which hold the camera-cc combination in the focuser tube to 'anticipate' the tilt before I turned the locking screw.

Am going to try your adjustments to see if I can get the focuser to hold without having to tighten the lock screw. Thanks for posting. There is hope...

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2 minutes ago, Uranium235 said:

you dont need to use the locking screw

Excellent. I think you ought to write the pds guide for removing the out of box nightmares. 

7 minutes ago, Uranium235 said:

no clear instructions from SW

Yeah. Even more surprised. They don't seem to have anyone on the ground, in the cloud or anywhere. If I have a problem with my Bresser, I send an e-mail to ES and they get back to me that day. Maybe I'm not comparing like with like but SW don't seem to do it like that(?).

Anyway, it's clear again tonight so I'm gonna stop feeling sorry for myself and go and take some snaps! 

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I am new in this site and i didn't get into all pages of this thread, but looking at few pages like first 2 and one in the middle and the last page it is showing how capable is that 130PDS, it is making me so thrilled and can't wait to get the budget sooner or later and order 200PDS as someone from another site recommended me to get [for visual purpose first and imaging second, without suffering with budget].

I hope i can figure out about collimation, i still don't know about it at all, but sure with search i can find out what is it and maybe how to control it somehow.

 

Keep posting your results, nice images and it will encourage me to get 200PDS regardless i didn't use my mount yet and just last month i got my equipment, funny!!!

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8 hours ago, TareqPhoto said:

I hope i can figure out about collimation

Hi and welcome. It's easy. As soon as you get to do it on a telescope, you'll see it's intuitive and will wonder what all the fuss was about. Some guides make a simple one-minute task seem horrendously difficult. So have a quick Google, but don't read too much about it before you try!

FWIW, I already had a 200mm telescope and got the 130mm because of the wider field of view. If you have a choice of which to get first, I'd recommend the 130mm.

Good luck and clear skies...

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22 hours ago, Stub Mandrel said:

the locking screw doesn't need to be so tight

Hi. I had a go at the tension but unless the telescope was pointing overhead, still couldn't get it to stop slipping . Even the slightest turn on the lock screw -not even trying to lock anything- and it tilts. You can't see it so much in a stacked image, but here's a light frame from the same; alas with the lock screw tightened...

 

m100-2.jpg

Edited by alacant
pereza
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1 hour ago, alacant said:

Hi. I had a go at the tension but unless the telescope was pointing overhead, still couldn't get it to stop slipping . Even the slightest turn on the lock screw -not even trying to lock anything- and it tilts. You can't see it so much in a stacked image, but here's a light frame from the same; alas with the lock screw tightened...

Hi

You might need to service the Crayford and try and see why it's slipping. I didn't have that problem with mine but later on I did attach a SW motorfocuser and they are very good at holding the focus and make it easy to make very small focus adjustments with changing conditions -plus you don't need to use the lock screw :)

Louise

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3 hours ago, alacant said:

Hi and welcome. It's easy. As soon as you get to do it on a telescope, you'll see it's intuitive and will wonder what all the fuss was about. Some guides make a simple one-minute task seem horrendously difficult. So have a quick Google, but don't read too much about it before you try!

FWIW, I already had a 200mm telescope and got the 130mm because of the wider field of view. If you have a choice of which to get first, I'd recommend the 130mm.

Good luck and clear skies...

Thanks!

I am getting only 200PDS and not 130PDS, because i have a plaxe in the future to get 80ED APO [triplet or doublet] scope, so 130PDS isn't necessary.

I think i will be that tool used for collimation, I think Cheshire or something like that collimator.

I think reading too much is making me confused too much, but it also helps me to understand many things in short time, the i take my time to understand each point slowly, and once i figure out what or how to do then i go for it, the problem is that each member has own experience or a way to solve and operate things and newbies are confused about which one to follow, and the most important thing for me is that English isn't my main first language, so i may understand 70-90% of what is written there.

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8 hours ago, TareqPhoto said:

I think Cheshire or something like that collimator.

Hi. Yes, a Cheshire is all you need, one with cross hairs is even better. There are a lot of idealised diagrams in the guides which look nothing like the real thing. Here's what it actually looks like through a 130pds looking through the focuser with and without the Cheshire.

1. Get the secondary more or less centred just by looking at it.

2. Insert a Cheshire with cross-hairs.

3. Use the secondary screws to make the cross-hairs intersect with the centre of the of the primary.

4. Adjust the primary to centre everything else.

5. Now go out and look at an out of focus star. Adjust the primary again tiny amounts to make it circular.

Forget all that. Just make it look like this:

IMG_20170521_180310.thumb.jpg.70a49c86b37f91b69f333960b463c348.jpgIMG_20170521_175701.thumb.jpg.ebc0d75a3bc39a8e2870cdb9a8bf79c0.jpg

 

Edited by alacant
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3 hours ago, alacant said:

Hi. Yes, a Cheshire is all you need, one with cross hairs is even better. There are a lot of idealised diagrams in the guides which look nothing like the real thing. Here's what it actually looks like through a 130pds looking through the focuser with and without the Cheshire.

1. Get the secondary more or less centred just by looking at it.

2. Insert a Cheshire with cross-hairs.

3. Use the secondary screws to make the cross-hairs intersect with the centre of the of the primary.

4. Adjust the primary to centre everything else.

5. Now go out and look at an out of focus star. Adjust the primary again tiny amounts to make it circular.

Forget all that. Just make it look like this:

IMG_20170521_180310.thumb.jpg.70a49c86b37f91b69f333960b463c348.jpgIMG_20170521_175701.thumb.jpg.ebc0d75a3bc39a8e2870cdb9a8bf79c0.jpg

 

hmmm

Ok, once i buy all the stuff and ready to use them then i will remember your tips, thank you very much!!!

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Hi everyone. Here's a light frame with the field deliberately tilted with the focus lock screw. It's distorting the stars, but not producing coma. Strange. This much tilt on my faster f3.9 and it would be coma city. Does anyone know what this effect is called? TIA.

Edited by alacant
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On 21/05/2017 at 09:41, alacant said:

Hi. I had a go at the tension but unless the telescope was pointing overhead, still couldn't get it to stop slipping . Even the slightest turn on the lock screw -not even trying to lock anything- and it tilts. You can't see it so much in a stacked image, but here's a light frame from the same; alas with the lock screw tightened...

 

m100-2.jpg

I don't have any problem with focus slipping without needing to use the locking screw and I have a 550D inside a cool box hanging off mine 1.25kg total so if you really cant adjust the tension to prevent it from slipping you may have a duff focuser... 

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On 20/05/2017 at 19:23, alacant said:

That's the problem; tighten it and it tilts the focus tube and/or changes the focus. The only way I could keep it flat was by trial and error between adjusting the two screws which hold the camera-cc combination in the focuser tube to 'anticipate' the tilt before I turned the locking screw.

Am going to try your adjustments to see if I can get the focuser to hold without having to tighten the lock screw. Thanks for posting. There is hope...

Might be nothing, but check that the 4 mounting grub screws( the outer 2 both sides of the plate under the focuser) are tightened down. I couldn't get the focuser on my 250 to hold until I noticed these were not tight.

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55 minutes ago, moise212 said:

 

I think this can explain what happens:

 

Hi. Thanks for the link. Yes, it looks like that on the right of the image. That's why I think the focusing lock is tilting the field.

That discussion was for field flatteners on refractors. Does the same apply to coma correctors on newtonian reflectors?

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59 minutes ago, Adam J said:

if you really cant adjust the tension to prevent it from slipping you may have a duff focuser... 

Hi. Thanks. It's only a matter of time, trial, error and a few cloudy nights before I get the right combination of twisting and turning to get the focuser o hold! The main issue is that the focuser lock tilts the field. If I can take the latter out of the equation, I think the issue will have been solved. Until...

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