lukebl

35 minutes ago, Adam J said:

Stop, nothing on that mount needs to be so tight as to be rounding off your Allen keys! You will strip something. 

Ok I've stopped!

Here's a video of the rattling. I've definitely made it worse, but not sure which action did it. Loosening and tightening the worm mesh nuts doesn't seem to make any difference at all. Fortunately I have another old (non-Rowan) NEQ6 I can use.

Thanks folks. I've done both things - checked the worm locking ring AND adjusted the worm mesh - and it's still rocking. In fact, something I've done has made it worse. The worm adjusting bolts are incredibly tight and have burred over a couple of my allen keys. Damn annoying!

Hi folks,

I've had my NEQ6 for a few years, and I've had the Rowan Belt modification done.

I can't say I've noticed this before, but the mount rocks noticeably back and forth in RA as this animation shows. Is this amount of play normal and can it be fixed?

I'm not sure why I haven't noticed it before, but it could account for the vagaries of my guilding although I do ensure that the mount is balanced heavy on one side to compensate for backlash. However, I would assume that the Rowan Belt should reduce backlash?

22 minutes ago, Pete Presland said:

Some nice details visible there

Thanks folks.

I haven't been posting any more recent Venus images, partly because the seeing seems to have deteriorated considerably since earlier in the month, and partly because of @CraigT82's awesome images putting mine to shame!

11 hours ago, JamesF said:

If it does need fixing then the alternative to replacing the filter is to go for the full fat mod and use a separate ERF in a larger aperture OTA.

Thanks for the input gents.

That's interesting as I already have an ERF from an incompleted PST mod with a TAL 100RS which I was never happy with. I'll have a go at  rebuilding it, although I always liked the wider full-disc view that the the basic PST gives.

I got out my old Coronado PST today, even though the sun is very quiet, to test it out and I noticed that the view was incredibly faint. Too faint to see anything at all really.

Could the ITF filter be the fault, as that seems to be the usual problem with PTSs? The pictures of rusty ITFs I've seen on the web show the filter looking very uneven at the periphery. However, mine looks fairly even right across as this photo shows. Perhaps the filter is so corroded that the corrosion has spread right across the filter?  I haven't had it out for at least 18 months.

Any ideas? I was thinking it wouldn't be worth fixing, but I've just checked the current price online, and maybe it's worth replacing the filter after all.

136108 Haumea is a Kuiper Belt object which was at opposition in Bootes last week, so I had a go at capturing it and measuring its light curve. My memory is terrible, as I've just noticed that I did the same thing a couple of years ago and posted it here on SGL but had completely forgotten.

Here it is anyway. What's interesting is that it has an ellipsoid shape and rotates fast (4 hours). In fact it's one of the fastest rotating large objects in our solar system. It also has rings and two known moons. There was a bit of a controversy about its discovery by Caltech in 2004. A Spanish team got wind of the discovery before it was officially announced and speedily rummaged through some earlier images and pre-discovered it, and claimed it. They later admitted they had accessed the Caltech observation logs but denied any fraud, stating they were merely verifying whether they had discovered a new object. Yeah sure.

Despite its vast distance, 49.5 Astronomical Units (Pluto is virtually nearby at just 34 AU distant), its movement was visible in this 3 hour stack of 4 minute exposures. Atik428ex, 200mm f/5 Newtonian. The bright star is mag 4.8 20 Bootis.

Here's the light curve. Quite distinctive, with a range of about a third of a magnitude from about 17.1 to 17.4 over the evening.

Here's its orbit and current position

Many thanks Andrew.

Here's a somewhat better presentation of the light curve. I've averaged out every 10 measurements (i.e. 10 x 30 sec exposures) and inverted the scale so that it reads better. I have noticed that asteroids often have a dip or peak in mid-rotation, so a rotation period of about 3½ hours seems about right.

I've been watching the close approach of Asteroid (52768) 1998 OR2, and have captured an interesting light curve. It's a 2km Amor asteroid, which swings right out nearly as far as Jupiter and passes within 16 lunar distances of Earth on 29th April. It's normally pretty faint, but I measured it at around mag 13 last night and it's predicted to get to around 10.8 next week, although by then it'll only be visible for southern viewers. It was in Cancer last night, moving at around 8 arc seconds per minute and speeding up rapidly.

I took 30 second exposures with an Atik428ex and 200mm f/5 Newtonian. Using Miniwin software, I generated this interesting varied light curve over a period of three hours, suggesting that it's quite irregular in shape. Wiki suggests that the rotation period is 3-4 hours, so I guess I've nearly captured a complete rotation. My measurement with Astrometrica indicated that its magnitude ranged from 12.7 at 20:40 to 13.1 at 23:00. Quite a significant range over a short time.

Here's a composite image showing its position at 5 minute intervals:

This is an image stacked on the asteroid using Astrometrica, showing its movement over 10 minutes

This is a straightforward stack with DSS, of 199 exposures. No darks or flats.

Finally, here's an animation of it at 5 minute intervals:

Sadly, I think that 99% of the public couldn't care less about the skies becoming more cluttered, and even embrace it.

On my village community Facebook page (very busy with the lockdown), someone has excitedly posted updates on viewing them and loads of locals are out watching them. No interest in protecting our natural environment whatsoever, and we should consider the skies above our heads as an integral part of the wider natural environment.

19 hours ago, Captain Magenta said:

....these indoor methods are a precursor (they get you into the ballpark) to the extremely more sensitive test of an actual star in good seeing, from where you can converge on perfection.

I do have one question: the step 1, can you not see where the laser strikes the secondary by looking at its 1st reflection In the primary? That’s what I do.....

No, unfortunately I can't see the secondary donut when looking down the tube for some reason. It's too dark down there!

On the point regarding a subsequent star test, surely that would simply tell you whether or not you'd collimated it properly, but wouldn't help you regarding the cause? If it proved that the collimation was still out, you wouldn't be able to tell whether it was the focuser, secondary or the primary which was at fault and you're back to square one.

5 hours ago, dweller25 said:

Yes it is possible to collimate your scope 🙂

@Captain Magenta posted this correct procedure earlier and it worked perfectly on my 6” CC......

I took 3 steps:...

Many thanks @dweller25 and @Captain MagentaI think I may have resolved the issue by a circuitous route to the same process using all available tools. Here it is simplified:

• 1. Use Cheshire to align the focuser with the secondary donut by adjusting the focus tilt adjuster. (I use the Cheshire, as I can't see the laser spot on the secondary. This wouldn't be a problem with larger open-tube RCs, where you can directly see the surface of the secondary).
• 2. Use the Howie Glatter with concentric circle attachment to align the secondary with the primary, so that the laser circles are central and evenly spaced across the primary.
• 3. Adjust the primary so that the 'tunnel of mirrors' viewed when looking down the OTA is equal when viewing from the left, right, top and bottom (see pic below). Even a slight misalignment will be clearly visible as the 'tunnel' curves upwards, downwards, leftwards or rightwards if misaligned.
• 4. Repeat stage 1.  Finished.

I may be completely wrong, but it looks good so far.

Re-reading all the responses to my thread, and looking closely again at my particular scope, I've come to the conclusion that it's simply not possible to collimate it properly for one simple reason: The focuser is attached to the primary and moves with it.

OK, you can align the focuser with the secondary, and then collimate the secondary. But as soon as you try and collimate the primary, the focuser moves with it and becomes misaligned with the secondary. Having a tilt adjuster doesn't help, as it's fixed to the same axis and moves with it. If you then try and realign the focuser with the secondary, then that puts the primary out again.

That Fullercope really is a planet-killer.

37 minutes ago, Mark at Beaufort said:

...When you state IR and UV are you using a filter to block this wavelength....

Actually, it's quite the reverse. The filter blocks everything except the UV. I bought mine a few years ago and have just seen how outrageously expensive they are now! Details here.

Great detail again!

Here's a couple of false-colour variations of Venus from the 10th April. The normal convention is to put the IR image in the red channel and the UV image in the blue channel. I had a go a reversing this convention. I think it's quite pleasing.

Captured with Baader U-Venus filter, c. 90,000 frames, of which 30,000 stacked. 13ms exposures @ c. 74fps.  3x Televue Barlow, Omegon RC8  and a ZWO ASI 290MM Mini Mono camera.

Aah! Don't remind me. I remember it vividly.

I went to bed early and was blissfully unaware. Next morning I noticed that there was an answerphone message on my phone. It was from a non-astro friend containing loads of 'ooh's' and 'aahs' and '*$*&*' and  'hey, are you seeing this?' as they witnessed the magical display. Needless to say, the following night there was nothing to see.

I have since seen the northern lights, but I had to venture all the way to the bl**dy arctic to see it.

That's a really lovely crisp image. Knocks spots off my efforts!

Technical problems meant that I didn't manage to get any satisfactory IR captures to make a false-colour image, but this UV capture shows some interesting cloud patterns. In particular, a bright patch on the limb.

Captured with Baader U-Venus filter, c. 15,000 frames. 19ms exposures @ c. 50fps.  3x Televue Barlow, Omegon RC8  and a ZWO ASI 290MM Mini Mono camera.

This is a capture from the evening of 7th April. I hadn't originally bothered to process the image because, due to various technical issues, I could only manage about 4000 frames before the mount went haywire and the laptop seized up. However, in an idle moment this afternoon I processed the frames and found that I'd managed to capture some unexpected detail. The contrasting dark patch above the centre and the pale area at the bottom were noticeable in individual frames. Maybe you don't need to capture tens of thousands of frames after all?

Captured with Baader U-Venus and IR filters, c. 4,000 frames for UV channel. 19ms exposures @ c. 50fps. Green channel made from 50% UV and 50% IR . 3x Televue Barlow, Omegon RC8  and a ZWO ASI 290MM Mini Mono camera.

Captured with Baader U-Venus and IR filters, c. 20,000 frames for UV channel. 16ms exposures @ c. 50fps. Green channel made from 50% UV and 50% IR . 3x Televue Barlow, Omegon RC8  and a ZWO ASI 290MM Mini Mono camera.

Cracking image. I'm amazed how you can capture 90k frames. It takes me long enough to capture 20k.

Sorry, I can't help you with this but it may be useful to know that the Howie Glatter circular pattern adapter is being made again. In the US I believe that Agena Astro, Starlight Instruments and Skies Unlimited have them in stock.

I've just got one myself, although it doesn't seem to be helping me with my RC collimation.

Some nice details visible this evening.

Captured with Baader U-Venus and IR filters, c. 20,000 frames for UV channel. 16ms exposures @ c. 50fps. Green channel made from 50% UV and 50% IR . 3x Televue Barlow, Omegon RC8  and a ZWO ASI 290MM Mini Mono camera.