Pitch Black Skies

These are the bearings if anyone decides to replace their own sometime;

2 × 30205M Timken Roller Bearing

6 × 6006-2RS C3 FAG Deep Groove Ball Bearing 30×55×13

4 × 689 2RS Ceramic Hybrid Ball Bearing 9×17×5

And I would recommend to at least  consider replacing the worm carrier bearings. They are the cheapest and make the most difference as the stock ones are simply junk IMO.

I've just replaced all of the bearings.

The new ones are a bit stiffer.

I'm really surprised that I got good guiding numbers last night. When I had the RA worm carrier off, I rotated the shaft in the housing and it was extremely notchy this time since tightening the nut/fastener.

With the new ones in, it rotates silky smooth.

Just need some clear skies to compare results.

2 hours ago, braybarr said:

I’m hoping this dew shield is effective

FWIW I've been using said dew shield for ~6 months. It has completely stopped the secondary from fogging up.

I'm assuming you are from Bray, Co. Wicklow?

I'm in Waterford on the coast so probably pretty similar humidity.

20 minutes ago, vlaiv said:

@Pitch Black Skies

Just noticed that you guide with 0.5s guide exposure. That is very fast and will often result in chasing the seeing.

Maybe try next time at say 2-4s just to see what soft of guiding you get?

Hey, na that's just the tracking rate at x.50. I have it set to 2s exposures. You can see it on the bottom right of the images. The layout is a bit different on ASIair compared to PHD2. It's not as sophisticated but it works 😅, sometimes.

So just had a chance to test guiding again..

A definite improvement since tightening the worm carrier nut/fastener.

I'm consistently getting a total RMS of less than an arc second now. This is great considering my image scale is 1.19"/pixel.

However, there is still the odd dip in the RA graph but it isn't as aggressive. I'm putting it down to those notchy worm carrier bearings. I will be replacing them soon and will be back with a further update.

It is great relief to have gotten to the bottom of it 🥳

Thanks for everyone's help

On 16/05/2022 at 03:34, braybarr said:

Can anyone tell me the size of the mirror stalk for secondary mirror? 

Hi,

I measured it in place so it's not exact but should be good enough for your purpose.

CS

Hi,

I measured it in place so it's not exact but should be good enough for your purpose.

CS

1 hour ago, starwatcher_ch said:

Maybe with a TSGPU it would be much better

It pushes the focus position up by 7mm when sat in the compression ring.

If you can screw it on to the focuser tube with an M54-M58 adapter it pushes the focus position up by 19mm.

Where these lines are flush with the white housing is where the focus position is.

I haven't included a line for when the cc is screwed into the focuser.

Well I know @Jamgood uses the GPU with the original focuser tube, but I think he uses a 294 with it. Not sure if that makes a difference.

12 minutes ago, starwatcher_ch said:

The only reason I don't own the TSGPU already is because of it's price.

I agree, very pricey indeed. But then look at the price of cameras, mounts, etc. In for a penny, in for a pound 🙂

In regards to cc spacing, I think @alacant would be your best bet there.

The problem with cutting the tube is number one the risk of the imaging train falling out. But it can also be problematic if switching to visual or if you ever decide to sell on.

43 minutes ago, starwatcher_ch said:

Much more than yours!

I have a feeling it might be causing reflections. 

Yes get the GPU if you can. It has the added benefit of being able to screw onto the focuser unlike the SW version. That alone will help with tilt problems.

I have to admit, I do regret cutting mine.

You live and learn 😁

12 hours ago, starwatcher_ch said:

But maybe removing the dew shield for focusing and flats isn't as problematic as I think...

Hi, I leave my dew shield in place for focusing and flats. I just pop the Bahtinov mask on top of it.

12 hours ago, starwatcher_ch said:

Would that produce such an effect? 

Unless you can see it tilting the imaging train I wouldn't have thought so. I keep mine fairly tight too.

How much of your focuser tube is protruding into the OTA?

This is mine at the focus position.

I shortened it with a hacksaw. I will spray the bare metal surface black in time. Just be mindful that if you decide to do this, when you rack out the focuser, its tube will no longer stop but will slip off the rollers. You might be able to just spray yours or flock it as I can see your star shapes are not affected by the drawtube protruding into the OTA.

This is a good video by Glenn Astrobloke for reducing reflections.

1 hour ago, starwatcher_ch said:

What causes these reflections?

I'm not sure, I haven't had this problem before with mine. I don't have my spider or OTA flocked either FWIW.

At a guess, they look like reflections of diffraction spikes. Could they be linked to your CC?

I noticed a vertical line through the horizontal line in the M57 image too.

@starwatcher_ch CS Karol, glad to see you've joined. But most importantly, that you've gotten to the end of the thread 😁

@JIm19130 I think you meant you have a 50mm guidescope.

Anyway, that set up will work fine.

A lot, if not most people use a 50mm guidescope with a 120mm camera for guiding.

I think I might have just found the source of the problem...

I found some play in the worm when rocking the mount from side to side looking for backlash in the RA. I couldn't hear the play and it was barely even perceivable, but after tightening one of the fasteners on the end of the worm the mount now feels more solid.

If the numbers are still poor, those worm bearings are the next to go 

1 hour ago, Clarkey said:

But the old bearings in the worm carrier were pretty awful when turning the drive wheel

Mine are a bit notchy too despite the mount only being a couple of months old. They might not be best quality to begin with.

I think I'm just going to do the worm carrier ones. They are cheap and besides, all of the others seem fine.

5 minutes ago, Clarkey said:

The small worm bearings were very rough

Did you get a chance to compare them to the new ones? Mine had a bit of lateral play. I'm wondering how much lateral play new ones might have if any?

Did you source yours through R&M BEARINGS?

Can you drop a line here after you've had a chance to test guiding to see if there's any improvement?

No improvement to the RA graph after adjusting the idlers and using a separate power supply to the mount.

I've tried various aggressiveness settings and they are not improving it much.

I decided to strip the mount down to have an inspection. My RA worm mesh is very tight again. I wonder if the mesh is too tight, is it capable of causing striction? ie causing the worm to jam for a split second and then release when tracking.

Anyway, I managed to inspect the bearings. There is a slight lateral play between the races on the larger ones. The smaller ones for the worm carrier have greater play. Is that that to be expected? Also when turning the worm in the carrier, I can feel very slight notches or bumps within the smaller bearings. It's hard to feel it but it is there.  I think this could be the source of the problem. I cancelled my new bearings order but might re-order just the 4 worm bearings.

Join the 130P-DS if you haven't already. There's a wealth of knowledge and experience there.

31 minutes ago, starwatcher_ch said:

What do you recommend for collimation instead?

I recommend a Cheshire sight tube/Concentre for collimating the secondary, and a collimation cap for the primary.

These are the ones I use;

https://www.firstlightoptics.com/other-collimation-tools/stellalyra-premium-cheshire-collimating-eyepiece.html

https://www.firstlightoptics.com/other-collimation-tools/rigel-aline-collimation-cap.html

14 minutes ago, Cornelius Varley said:

No, it's a Newtonian reflector. 

Yes, you're right. The AM 114 is a Bird -Jones. The 130 doesn't have the correcter, just the spherical mirror.

On 10/05/2022 at 17:23, starwatcher_ch said:

1. replacing the 2" screw adapter with the original adapter/compression ring adapter for each laser collimation

I'm not a fan of lasers anymore due to their inability to help with rotation of the secondary mirror. You could literally have your secondary twisted a whole 45° and with enough adjusting of the collimation screws still get the red dot in the centre of the primary.

But sorry, to answer your question I think you will need to replace the screw in adapter with the compression one for each collimation or maybe just go back to the compression ring.

A third thumbscrew tapped into the compression ring ensures a more concentric fit when tightening. Definitely something to do if you haven't already.

If keeping the screw on adapter, you could try screwing the whole imaging train off in one go and have the laser and compression ring etc pre-assembled and ready to be screwed on in one go.

Is the AM 130 a Bird-Jones design with spherical mirror? I've heard nothing good about that design.

If it is, I reckon the 130P-DS would be a definite improvement.