ollypenrice

2 minutes ago, vlaiv said:

I was just pointing out that larger scope means more aperture, and as such has benefits for target resolution - it will collect more photons and will be faster.

 Larger scope means more aperture? Damn, I hadn't thought of that!!! 

Seriously, I think everything I have to say is included in my first post which is strictly devoted to comparing 12 inch F4 and 16 inch F4. Where, in your view, does the 16 inch win in seeing which is limited to, say, an arcsec per pixel?

(I always enjoy our disagreements!)

Olly

1 hour ago, vlaiv said:

Same difference Although "speed" of the scope stays the same, "speed" is not really the speed of gathering photons. Best to think of it as "aperture" at certain pixel scale. As you pointed out, both scopes will over sample on most cameras (pixel sizes) and there will definitively be some binning involved to get to proper scale. If we consider that, then both scopes can be matched with a camera and bin factor to produce same target sampling rate.

16" vs 12" at same target sampling rate - more photons in first case.

Another important fact to consider with this type of reasoning is available FOV - longer FL will reduce FOV, so that should be taken into account when considering scope.

Isn't that exactly what I said???

lly

Just now, vlaiv said:

There is a lot to be gained by using 16" F/4 scope (I'm guessing it is F/4 scope because you mentioned 1600mm FL).

Take for example difference to my 8" RC. I use it with ASI1600 - it's oversampling at 0.5"/px, but binning sorts that out, and I usually consider my images to be between 1.5"/px and 1.0"/px (x3 or x2 bin).

16" F/4 scope will work with the same sampling rate as my 8" RC, but will have x4 light gathering capacity. I would not mind having a scope that will gather x4 more light and keep similar "properties" as my current imaging scope.

That's not what I'm saying. Note that I'm comparing a 12 inch F4 with a 16 inch F4, not a 16 inch with the same FL as the 12 inch. The question is not whether a small scope and a large of the same focal length will be equivalent. They won't, as you say. The question is, what will the OP gain by moving from a 12 inch F4 to a 16 inch F4 bearing in mind the FL will increase? In my opinion both will be seeing-limited and risk resolving detail at the same level but with a loss of FOV in the large one. 

Olly

What do you expect to gain from the 16 inch for deep sky imaging? The 12 inch has a FL of  1.2 metres. The 16 has a FL of 1.6 metres. A FL of 1.2 metres with modern cameras will easily take you to an image scale of below, or even well below, an arcsecond per pixel. What resolution will your sky support?  If it will support scales below an arcsecond, at least on any kind of regular basis, I'd be amazed and would be similarly amazed if the theoretical gain in optical resolution would translate into new details resolved on the image. We are seeing-limited.  I'm struggling to find much improvement in resolution when comparing data from a 5.5 inch refractor at 0.9"PP with data from a 14 inch reflector working at 0.6"PP. (Different cameras.)

I ask this because the big scope is part of your mount game plan. Personally I'd go for the bigger aperture for visual but not for imaging. I can't see the point. I think you'll end up with the same final resolution and a smaller FOV.

In any event, even the 12 inch can take you into imaging territory where you'll want a guide RMS of 0.4" and that's a high level of precision. For me the EQ8 is a big hefty mount more than it is a high precision one and for that reason I'd go for the iOptron. (That is if I couldn't find a second hand Mesu. Both mine cost less than the new price of the iOptron.)

Olly

Are Mesu mounts attractive? You bet they are.

Olly

On 28/03/2019 at 10:46, carastro said:

Bit late to the party here.  But I was told to add a type of grease to the bolts, I can't remember the name of it right now, but I know it has the name of the metal in the title.   I think I know where it is and will look it up once I can get out to the observatory.  

After adding this grease I found my bolts on my NEQ6 (that I used to own), would turn more easily.

Just looked up metals, and I think it might have been copper grease, but will confirm later.

Carole 

 

Copperslip!

As has been said, tilting the mount slightly is the obvious answer. While a mount which isn't level E-W may need more iterations of the drift method since the two axes will interact slightly, being tilted N-S has no effect whatever on anything (provided the thing doesn't fall over!) How does the polar axis know it's been tilted by the pier-tripod or by the pivot? It doesn't. They are equivalent. (The Avalon has a linear bubble level on the E-W axis only.)

Olly

8 hours ago, Trikeflyer said:

Thanks for your input so far folks it’s helped. I think based on research so far  it’s between the Leica and the Nikon Monarch 7. Does anyone have a Nikon Monarch 7 who could give an opinion?

steve 

 

I've made this comparison back to back. The Nikons were sharper and more contrasty, which sounds like a clear bonus and in some ways was. However, the Leicas gave a more natural view, significantly so to my eye. With three of us involved in the test it came out as a dead heat, one for the Nikons, one for the Leicas and one undecided. Hey, that's a big help!  The Leicas of mine which you tried were eleven years old when I bought them about five years ago. I don't know how significant that is.

Olly

2 hours ago, Craney said:

 

So    @ollypenrice   , if you are thinking of moving over to Dusk then maybe wait a week or so just in case.

 

 

I'm not! Artemis Capture is perfect for me but I'm sure that, between them, the software brigade will oblige me, in the end, to switch to something they tell me is better.

Olly

8 hours ago, Jkulin said:

Hi Olly, thanks for your thoughts, I'm not looking for a replacement for my main imaging, as PHD2 works very nicely, I'm looking for an option to guide without my laptop for widefield with my SA and Sony A7RIII with a few lenses, I could use the 500 rule and go unguided, or like I did a couple of years ago where I got 450sec subs with no guiding and hardly any discernable trails, but I would like to keep things simple when travelling and really without a laptop would be a blessing due to my bad back.

Ah, then if you want to dispense with the laptop it will have to be a standalone guider. Probably worth a punt in that case. I'd just check that the one you go for will allow single axis guiding. I don't know the guiders in question well enough to be sure about this.

Olly

The standalone guiders may seem like a painless way into guiding but all your eggs are in one basket and if it plays up you might wish you could change baskets! Personally I think they solve a problem which doesn't exist and risk introducing new ones which do. Reading the threads over the years some people find they work fine, others struggle.

Personally I'd just go for a finder-guider, ST4-equipped camera and PHD2 on the laptop (assuming you have the necessary USB ports.) PHD2 will auto calibrate and you can refine this by using the Guiding Assistant after that. You'll need to disable the Dec guiding facility or it will refuse calibration, but that's in the 'Brain' section of PHD.

Olly

Provided your dovetail bar were a light one I would expect a camera and 200mm lens to manage with no more counterweight than the bar itself, though you could tape a metal bar along it for a little more weight if necessary.

We've run cameras without counterweights on our EQ sixes here several times here without issue.

Olly

Firstly your FITS headers should show which filter was used for which capture so you can, albeit laboriously, go through them all and put them in the right place. (I would make a separate folder for each filter and asign each checked image to the right folder rather than rename the files. That's just me.)

I haven't used Dusk and don't want to because there is nothing wrong with Artemis so far as I'm concerned. However, could this have anything to do with the nature of the sequence you've chosen? Normally with sequencers you can scroll 1,2,3,4 etc or choose 1,1,1,1, 2,2,2,2, etc.

Olly

I wish I'd seen this thread earlier because last night our LX200 14 inch wouldn't align. Fortunately one of our guests had seen the thread so we stopped trying! It seems absurd that one cannot input the time, date and location without the GPS. Is this really the case? Time to see what the manual says on the matter.

Olly

If you have to slew away you can do two things to get back on target. Once framed up you can save the position as a User Defined Object and then 'Go To' it again or you can note the framing's RA and Dec and drive back manually to those co-ordinates.

Unlike Souls I frequently find that I have no star suitable for a B-mask in my target FOV, especially in narrowband. However, I only use the B mask for an initial focus while aligning the mount. I then focus using the FWHM feature of my capture software. Full Width at Half Maximumum is a universally popular focusing routine available in most capture software. Over bright stars with saturated cores are not suitable so it works fine on faint ones.

Olly

My first scope, a TAL Newtonian reflector, did come with a solar projection kit (including little clips to hold a card so you could copy the sunspot positions onto it.) I didn't use it a great deal but never had a problem. However, I'd err on the side of caution regarding heat build up at the primary.

Olly

1 hour ago, Davey-T said:

Reminds me I bought one of those bright red power packs once, damned if I can find it anywhere 

Dave

That's cos all astro kit is now bright red!

Olly

Exciting. Just a thought on the American plug, but US voltage is 120. Doesn't this cause a problem?

Olly

23 minutes ago, Philip R said:

As long as you check the filter for defects, i.e. pinholes, rips, securely attached to your OTA or 35mm/DSLR lens, etc., before each and every use, solar safety films are perfectly safe. Also worth mentioning that you should make a solar filter for your finderscope and/or RDF - better still, remove either or both before viewing and use the shadow for alignment. 

Another neat idea is to make your own pinhole solar finder. There are some ideas further down this thread. 

Peter Drew's is a good method. Some people make their solar finders adjustable in angle to align with the viewing scope but the easiest way is to align it roughly, get the scope pointing at the sun, and then just mark the sun's central position on the finder screen you've made.

Olly

The Baader film might actually be safer because it is a double sided filter. Once it's delivered it should be fitted into a permananent ring the size of the scope's aperture so that it undergoes no further crumpling and it should be cared for properly, stored in a box etc. When fitted to the scope it should have permanent ties holding it in place against wind or knocks. It can be easily checked for pinholes and these can be blacked out. They won't show for the same reasons that a secondary mirror doesn't show.

Remember to block finderscopes, Telrads, etc., or you can get a nasty burn at the focal point!

If you really are worried you could try the projection method. Google solar projection and you'll find many ways of doing it.

Olly

Argh, the suspense! I look forward to your comparison since I know the Lunt 60 quite well.

Olly

From the review: We achieved this using a 1600 ASI camera; changing to an imaging camera with a smaller sensor meant that the telescope was able to get quite close-up images too

Whoops. 

Will this instrument show proms or is it strictly for the disk? It does look very tasty and I'm following with interest.

Olly

On 17/05/2019 at 00:09, cotak said:

For mono work you'll really want an auto focusing solution. Actually for OSC you might want that as well. 

 

Focus can drift on any telescope so reliable autofocus saves effort once you've got it working. Personally I focus manually but I'm old fashioned.

However,  I don't believe non-parfocality in mono systems comes from the filters but from the optics, so a mono allows you to refocus per colour if you wish while an OSC does not. As has been suggested already, in mono imaging the filter needing perfect focus is luminance (and any NB you shoot.)

OSC is slower than mono because it cannot shoot luminance, which is catching R, G and B simultaneously so is extremely fast, and objects which are strong in Ha build efficiently in a mono rig.

Like Carole I found OSC data to be rather difficult to process to any kind of good standard. Certainly harder than LRGB. Making an RGB in AstroArt goes like this:

1) Stack the R,G and B separately and have them open. 2) Use auto-align to align them in one click. 3) Use Trichromy, click auto white balance and auto colour balance and say Go. If this takes a minute I'd be surprised.

Olly

I do absolutely need the one marked, Hello darkness my old friend. Where do I look????

lly

1 minute ago, FLO said:

I hope our customers in France don't start feeling that way 🙃

Steve 

My purchasing policy is now up for review!

😀lly

41 minutes ago, Adam J said:

Would be interested in AD 5nm vs Baader 4.5nm vs Baader 7nm if possible with regard to reflections more than anything else. 

Adam

I've never had reflections in any Ha filter, Adam.

Olly