dweller25

13 hours ago, quasar117 said:

The closest example to what I'm seeing when in focus on a star is as per this image although the black spikes are more severe in this image than what I'm seeing. 

Yes, apart from the spikes that is how Aldeberan looked tonight compared to the dimmer stars in the same field of view - but with an airy disk.

@quasar117

I have just been out with the Takahashi 4” F/8 refractor.

Jupiter at 11’ high is too low for any meaningful observation now for me.

I spent some time looking at Aldeberan which was 24’ high at x150 power.

It appeared bright, unsharp and unsteady, the dimmer stars in the same field of view were more stable and sharper.

At perfect focus Aldeberan showed an unsteady airy disk, either side of focus did show an unstable airy pattern that was identical.

This is just a data point for you to compare with your observations 👍

To summarise, this is what I would expect from poor seeing and low altitude observing.

Had to observe from the conservatory as I have a bad back, so had a very limited view and could not look any higher !

See here

https://www.cloudynights.com/topic/611161-doubts-about-taka-fc100d-star-test/

But - all that matters is the image at perfect focus 👍

Are you seeing any of these ?

9 minutes ago, quasar117 said:

Yes I'm going try directly mounting the EPs to eliminate the diagonal from the equation.

The sky isn't looking great here at the moment, looks like a good chance of rain soon. 

Should I see an airy disk both inside and outside of focus? As yesterday I could only see it when racking the focuser in.

Pick a very high star for best seeing

Yes, perhaps the better compromise would be F/5 ?

Moving thin clouds = not the best conditions.

It may be better tonight, I plan to take out my 4”……….

21 minutes ago, DAT said:

Thanks for the replies, I think I need M4 x 35mm stainless steel screws. Have found some fairly cheap on eBay (about £6 for 5). Will leave the washer modification for later as I think collimation is looking good for now, might even be able to see something in the next week or so…

Collimato perfecto 🙂👍

Hello @powerlord 

It’s fine not to go out every clear night - that can be hard work - it needs to be FUN 👍

You are not alone the S.A.D thing is easily developed over the winter, but spring is here now and the weather is getting warmer 🙂

I would suggest a gentle reboot with a pair of Binoculars or perhaps use your 90mm refractor for some visual stuff. 

How about moving to a bit of Sun observing/imaging ?

As long as you enjoy it you cannot go wrong.

Really nice images 👍

The seeing on Tuesday evening was VERY poor.

Even Jupiter was twinkling to the naked eye 😱

Good luck Rob 👍

 Vulcans always tell the truth 🙂

There is also a 7mm Pentax XW, which barlowed will give x285 🙂

15 minutes ago, ollypenrice said:

Have you tried blowing air across the surface of the mirror? There's an argument which says that this is the best way to break the boundary layer.

I've never tried it and no longer have a Newt.

Olly

I fitted a fan on the back of the Newt and pulled air out, it immediately removed the boundary layer 👍

There is a 5mm Pentax XW in the for sale section 🙂

Looking good 👍

My findings are about the same as @vlaiv’s calculations.

90% of my observing is planetary.

I find maximum useful magnification is 1.5x the aperture of the telescope in mm’s.

So the 100mm refractor would ideally be x150, but I often go to x180 !

The OO 1/10th wave 200mm F/6 Newt would ideally be x300, but I rarely go past x250 !

Magnifications beyond the “ideal” show a bigger image but do not show any more detail.

However, UK seeing conditions can often limit this to around x250 or less sometimes.

Exit pupil also plays a part.

12 hours ago, Carbon Brush said:

Interesting to note.

Looking when the OP last visited. There has been the opportunity to look at all of the questioning and helpful posts made earlier than this one.
No photos or other scope/eyepiece information, or 'fixed now' thanks, reports have been forthcoming from the OP.
I have noticed a lot of 'help' posts being made by new members, usually followed by lots of helpful advice from established members, sometimes with requests for further information.
But all too often the new member does not respond.

In this thread a great deal was made of @900SL response.
Although some would not consider it to be the best worded response. It does comprise valid content.

OK moan over.

The OP revisited a few hours ago, hopefully he/she got the information needed from the constructive posts.

What a classy looking scope John 👍

Hello and welcome to SGL 🙂

Not in the same league as above but my oldest astro book is “Astronomy with Binoculars”, James Muirden, 1976.

Thanks for the heads up 🙂

I think truss designs are slightly heavier than solid tubes for the same mirror size.

16 minutes ago, Adreneline said:

You probably don't want to hear this but I found I couldn't get a satisfactory collimation with the stock focuser unit - too much droop from the draw tube.

I also had this issue !

So you may need the tilt plate.