Ricochet

I think that the best tool for positioning the secondary under the focuser and aligning it with the primary is a sight tube. Most modern Cheshires are combined Cheshires and sight tubes, and the red FLO Cheshire is an excellent and accurately machined example. For aligning the primary the easiest accurate tool is the barlowed laser. You want a laser that you can collimate with a 45° face and a decent barlow that is accurately machined enough not to tilt in the focuser. I also use a small Cheshire with the sight tube crosshairs removed to check the primary (I can also use this in place of the barlowed laser but it requires more practice).

With regards to the Hotech, I did once buy one, but returned it to the seller because the self centring and/or collimation was off and it did not give repeatable results. I was also unimpressed with the quality of the laser image it projected. If you are going to buy an expensive laser for alignment of the secondary I would go for a Glatter option.

7 hours ago, bluesilver said:

Bit of at a loss on what i can do to improve it to at least make out the moons as small disks.

Practice, I think. Changing scope won't make them any bigger unless you also increase the magnification, and you can do that more cheaply with eyepieces. As it stands you can already get 240X and 300X which might be too much for Jupiter itself and that really is the interesting object. I would be more inclined to get an eyepiece or binoviewer set up equivalent to 7mm. 

I use RACI and Telrad. It is important to think about the positioning of the two units before fitting them. I think that you want the RACI situated so that you can use it from the same position as you look through the focuser and switch from one to the other easily. Unless you have a very large scope this means putting the Telrad on the far side of the RACI so that it doesn't get in the way. 

What eyepieces do you own? I don't know why you're talking about other scopes as really the only two explanations are not using the correct magnification or, more likely, observer experience and eye "criticality". The scope you have is a good one and not going to make small disks into point sources. The only thing would be if all your point sources are fuzzy balls, in which case I would recommend masking the edge of the primary mirror to tighten things up.

23 hours ago, Lockie said:

My Android devices either didn't work at all or worked very un responsively, sometimes slewing out of control heading for tripod collisions!

Which devices did you try? Some android devices have cheap(er) screens which tend to stop working properly when they get cold, which is a bit of an issue if you want to use them for astronomy.

On 08/07/2019 at 14:49, M55_uk said:

I have just the standard eyepieces that came with the scope - 10mm & 20mm celestron.

I am hoping to be able to get better view of planets and moon to start with. My reading tells me that Barlow may not be as useful for DSO. Is that right?

A barlow may or may not be useful for DSOs depending on the focal lengths of the eyepieces used with it. For observing DSOs you will want to pay attention to the exit pupil produced by your telescope-eyepiece combination. From a light polluted area you probably don't want to have an exit pupil greater than 5mm, but you might want to go a bit larger to max out your field of view with a 30/32mm Plossl, and you can go as low as 1mm for DSOs that resolve into point sources (i.e. star clusters) if they fit within the field of view. For extended objects (galaxies, nebulae) the acuity of your eye makes a 2-3mm exit pupil ideal. To find the exit pupil simply divide the focal length of your eyepiece by the focal ratio of your telescope (5). If you use a 2x barlow then you effectively halve the focal length of the eyepiece so both your 10mm eyepiece and your 20mm eyepiece plus a 2x barlow will give you an exit pupil of 2mm, which is ideal for DSOs. On the other hand, your 10mm plus a 2x barlow will give a 1mm exit pupil, which is at the limit of usefulness for some DSOs but in the right ballpark for planetary observing. 

With regards to your current eyepieces, I would be looking at replacing both with better alternatives in addition to your planned barlow purchase . A 23mm Aspheric can be found cheaply on eBay and is an optically sound eyepiece. For higher magnifications I would suggest either:

• 10mm Aspheric, 7mm Skywatcher Planetary, 2x barlow
• 12mm Plossl or Starguider, 8mm Starguider, 2x barlow

Which I think would have you quite well covered. Higher priced options are available if your budget stretches either now or later. I think any of the barlows previously mentioned will be optically similar so it comes a bit more down to construction. One with a removable lens cell that can be screwed directly to the filter threads of the eyepiece would give about 1.5X so you could skip the higher power (lower focal length) eyepiece in my suggestions initially. Otherwise I would look for a decent size thumbscrew that is easy to use with gloves and a compression ring to prevent damaging the eyepiece barrels, unless you're more concerned about price in which case the one @Cosmic Geoff mentions is very nice optically and available direct from China very cheaply (without the "Skywatcher" branding).

1 hour ago, M55_uk said:

Thanks John.

I have read that these ES Focal extenders need longer in-travel of the focusser. Has anyone on this forum used the ES Focal extender with the Celestron 130EQ?

I think that is only in comparison to powermates rather than generic barlows. 

With regards to the barlow, what are you looking to get from it and which eyepieces do you already own? 

10 hours ago, MKHACHFE said:

Is the general consensus a yes? It's an interesting question to be sure. I told my wife the other night that the colour in the beautiful astrophotography images we see is fake, so she asked what the REAL colour of these DSO's are...and i had no answer. Is there even an answer? I know most of the detail in the images comes from wavelengths shorter and/or wider than visible light. 

Not necessarily true. Most of the matter in the universe is hydrogen so much of the emission is Ha emission. As an example here is is the visible spectrum for the Orion nebula:

http://stars.astro.illinois.edu/sow/ori-neb-p.html#spec

You can clearly see the Ha, OI and SIII lines in the spectrum as well as the Hb and OIII lines. When you look at the nebula through a telescope you might see it as green, but in photos it is mainly red and the reason for the difference is the difference between your night and day vision. The graph below shows the sensitivity of the three different colour cone cells used during the day and the rod cells used at night (dotted line):

So you can see that if the nebula was bright enough all of the red emission would be seen by the red cone cells, but because it is dim, they aren't triggered when we view it through a telescope. We can however, detect some green, because the green cells and rods are much more sensitive at the Hb and OIII wavelengths. For dimmer nebulae only the rods are stimulated and hence we only see them in black and white.

18 minutes ago, Roadrunr said:

thats correct, I did not clean the outside, ok I had too, I will show you a foto made with this scope.

If that photo was taken by holding a phone to the eyepiece, you need to clean the eyepiece, or as @John says, the diagonal mirror. 

If you're carrying it up and down flights of stairs I think you will need to go lighter. The 8se linked above states 11kg for the scope and 4kg for the mount, do you think you can easily carry that in one go or is a lighter set up needed? As I said in a similar thread a few days ago, I think something that can be carried in a backpack is probably a good idea, although aperture will be reduced compared to the current scope. 

The dust visible in the photos looks like it is on the front of the corrector plate and the inside looks clean so there is no reason to open it up as far as I can see. Even if the dust shown is on the inside there isn't enough of it to make a difference when you are looking through the scope. 

Good luck 

Are all your wires still connected to the rotary switch? Getting in there looks to be the hardest part. I can't get a picture and I'm trying to see what goes where using the diagonal mirror. 

Wiring is as follows: 

Red: Battery pack + to reticule top

Black: Battery - to switch, 1 position clockwise from unused pin

White: reticule bottom to switch, 1 position anticlockwise from unused pin

The pattern of the marks does indicate fungal growth so I think you would at least want to look into cleaning the mirror with something that will stop that. I'm sure someone will know what works best. As for recoating, that may or may not be necessary. It takes quite a bit of damage on a primary before it noticeably affects the view, you will most likely notice it if the damaged areas are shiny like scratches would be. 

With regards to the bright cross, that would be the diffraction spikes due to the secondary spider, just like you get with bright stars but wider as the planet is wider. I would guess that you usually observe at higher magnifications where the spikes are less visible but conditions have meant you have used lower, brighter magnifications. 

1 hour ago, Ben the Ignorant said:

you're looking through an O-III filter which makes the background so black the deep-sky object's color is not as difficult to discern because of stronger contrast

Given that an OIII filter only lets through a few nm of green light, anything viewed through an OIII filter will be green, no matter the spectrum emitted by the object. 

Ideally, the centre spot would have a hole in the middle which will make aligning the centre mark with the shadow of your collimation cap easier. However, as you have already put the dot on your mirror I would be inclined to leave it in place as removing it is the operation where you are most likely to scratch the mirror (even if it his behind the secondary shadow). 

10 hours ago, doubledoubleswifty said:

tedious to set up

What do you mean by this? Just putting the OTA onto the base and screwing in the handles or is there more to it? 

Judging from the logos I'd guess the pro version but either plus or pro will allow you to enter your equipment to show field of view and/or Telrad overlays. Here's mine (SS5 plus) showing the correlation between the Telrad circles (red) and a standard 9x50 finder (largest blue circle) and some of my eyepieces when used in my dob (smaller blue circles). 

I agree with @Stu that learning to find these brighter objects with your current equipment is the first step. 

If you have the standard straight through finder then both your scope and finder have an inverted view. 

7 minutes ago, MSammon said:

John why exactly do you think you sometimes get better views with your refractors over your 12 inch dob? Are they 4 or 5 inch or what? 

See @vlaiv's post on page 1: 

On 24/06/2019 at 23:42, vlaiv said:

In principle bigger aperture is always better (all other being equal), but there are circumstances when smaller aperture provides more pleasing image. This happens in poor seeing when atmosphere is turbulent. Larger aperture is gathering light from larger part of atmosphere (larger cone) and it will be impacted by seeing more than smaller aperture (you can effectively imagine both scopes gathering light thru column the size of aperture

27 minutes ago, MSammon said:

Is there a calculation for determining at what point a reflector aperture size beats the contrast of a refractor of a given size?

I don't think contrast works like that. You are fighting diffraction from the secondary obstruction so the only way to beat a refractor would one to have a negatively sized secondary, not something that you can achieve in the real world. All you can do is reduce the secondary to the size where it isn't really noticeable. From memory I think it is about 20%. 

40 minutes ago, MSammon said:

How to improve contrast with a reflector?

The best mod I ever made to mine was to add a baffle to mask the edge of the primary mirror. You lose a couple of mm in aperture but you lose the part where the mirror is hardest to figure and the coating quality is worst which removes scatter. 

There is no one eyepiece that will do everything. Different targets will require different eyepieces to get the best view. To start with you should just use the eyepieces that came with your scope to get an idea of what they can do and what you are missing so that you know what you're looking for from your first purchases.

Based on my own eyepieces I would say that you want to be looking at an eyepiece collection that looks like the following:

1. An eyepiece with a focal length around 2 - 2.5x your focal ratio (10-12.5mm)
2. An eyepiece at least 2x the length of #1, so 4-5x the FR (20-25mm). This is also going to be your widest field unless you live under dark skies so you may want to get something like a 24mm 68° eyepiece which will max out the field of view a 1.25" eyepiece can have (however, your telescope could use a 2" eyepiece here if you wish)
3. Eyepieces shorter than #1, stepping down the eyepiece focal length in steps of 1.4x until you get down to an eyepiece with a focal length roughly equal to your focal ratio (5mm), maybe a little shorter. This will mean 2 or 3 eyepieces, or the first "step" and a 2x barlow will give you the same lengths.

This should set you up quite nicely for DSOs, but for planetary you will want more options as how much you can push things is very dependent on the atmosphere. A decent zoom and barlow combination is probably going to be the most cost effective option as you can just dial in the optimum magnification the conditions allow, otherwise you will need a few eyepieces with similar focal lengths at the top end of magnification, i.e. 5, 4 and 3mm, maybe some between.

It's looking good for most of the UK tonight. I think you'd at want to at least get the dob out to cool down unless you're planning on concentrating on double stars. 

Where do I need to be looking for that sort of deal? 😮

Google for barlowed laser collimation, much more accurate than a simple laser and your switch issues will have no impact (unless you mean sometimes it won't turn on).