Ricochet

There are really three things to consider here:

1. The maximum magnification your skies will support
2. The maximum magnification that your telescope will support
3. The smallest exit pupil that you can comfortably use.

The first one, I can't be a great help with as i have no knowledge of your skies. However, in the UK  , under the jet stream, we often say 200x-250x is about the limit and I don't know of any reason why you can't also reach at least this. I see you have an 8" dob listed so you should have a pretty good idea of the magnifications that you have used with that. Anything that has been useful with the dob is a magnification that your skies can support (at least on some occasions).

Moving onto the magnifications that the scope can support, which is what you were really asking about, we can start with the "traditional" limit, which is 50x-60x per inch of aperture. These days everything about your scope is measured in millimetres so it is probably more useful to convert this limit to 2x-2.4x per mm of aperture. However, we can't just take this as gospel and apply it to all scopes, but remember that it was devised using long focus achromatic refractors solely for the purpose of splitting double stars. At the top end of magnification, where the exit pupil is small, the image is dominated by diffraction and the Airy disk is visible around stars. Any scope design with a central obstruction has more diffraction and so I suggest that telescopes with a central obstruction, and short focus achromats which are dominated by CA and SA, have a lower limit. Additionally, most people want high magnifications for viewing the planets for which the traditional limit is often revised as the more conservative 25x-30x per inch, or 1x-1.2x per mm, of aperture. I'm not sure quite when this new limit came about, but suspect that it is partly a result of the increasing use of larger, centrally obstructed designs that have more diffraction and are more likely to hit atmospheric limits. For your ED refractor (a design superior to long focus achromats) I suggest that you are looking for a planetary limit somewhere between these two given limits.

Finally, we have to consider the exit pupil and your eye. The exit pupil size can be found easily by dividing the focal length of the eyepiece, by the focal ratio of the telescope it is being used in. Converting the limits above gives us corresponding exit pupil limits of 1mm-0.85mm and 0.5mm-0.42mm, which equates to a eyepiece focal lengths approximately equal to the focal ratio of your telescope, or half of it for quick in the field selections. As well as the image becoming more blurred due to diffraction as you decrease the exit pupil, you will also notice an increase in the visibility of "floaters" in your eye(s). This will vary from person to person and there is no real way to determine where your limit is, aside from trial and error. If you want to reduce the effect of floaters at high magnification then using binoviewers will help, as your brain will use the signals from both eyes to filter them out.

Your current 6.7mm eyepiece gives an exit pupil of 0.89mm, so right in that lower limit, so with an ED refractor, which I think can push those limits I would definitely give a 5mm a go.

31 minutes ago, discardedastro said:

Not as such - but you can get an "erecting prism", which will do that (and fix left-to-right, too). But I've never used one - mostly seem to be pitched at terrestrial use rather than astronomy.

That won't work with a Newtonian as there will not be enough focuser travel to achieve focus. 

I wouldn't worry about getting the image the right way up, you soon get used to moving the scope and when viewing astronomical objects the orientation doesn't matter. 

The dob is a much larger scope. It would probably be worth seeing one in the flesh before buying. It will outperform the other options on all targets but will be difficult for your kids to use. 

11 minutes ago, Mr niall said:

Thanks, but I think spending more than my entire budget on a single eyepiece is perhaps not the way to go...

Sorry, I keep forgetting the prices these days. A 23mm aspheric would be a much cheaper alternative. 

5, 8 and 12mm BSTs. They are the best three Starguiders, the longer ones are not going to perform well in an f5 scope and you should look at the ES68 range instead. 

When you try to focus on stars turn the focuser so that the circle becomes smaller. When the circle is at its smallest, or even a point, you are in focus. The point at which stars are in best focus will be almost identical to the point at which the moon is in best focus and you may not be able to tell the difference between the two points. If you find that one is in focus but not the other, you are mistaken about one of them being in focus. 

Chris, what is your budget for this scope? The scopes listed above appear to be around the £100 mark but the Heritage 130p you were looking at is a bit above this, does that mean there is some leeway?

Also, am I right in thinking that whatever you buy has to include a mount as you don't have one/can't get on with the EQ you have?

2 hours ago, Lockie said:

The white with green accents livery looks great, and I dare say that mount and tripod must be the lightest from SW yet? I especially like the look of the 130p variant. I would be interested in this one especially if it had the motor drive. These could be very nice grab n go's indeed,

Looks like one for your review list then.

It would be interesting to see how these compare side by side with the az-eq Avant line. They've combined a couple of the same telescopes with the same mount head but changed the tripod, added longer slow motion controls and added a dovetail clamp. It seems like a difficult choice between the two.

So long as your scope has rings and a dovetail it shouldn't be an issue. If it is for visual I think an alt az mount is better for a Newtonian. 

1 hour ago, Vondragonnoggin said:

Ive seen it posted a lot of times that the moon when viewable in the daytime is just as bright as at night so no filter is needed but none of the people posting that have light sensitivity issues. It’s the contrast between dark and light that brings out the sensitivity.

How do you find the moon with binoviewers? It seems to me that viewing the same brightness with both eyes negates the issue, but I don't have a general sensitivity issue.

20 minutes ago, Jazzo111 said:

Cant pay more than 20 pound strict budget over payed on eyepieces lads lol

2"

1.25"

Cheaper 1.25", don't believe the before/after filter image.

I agree with John, a Neodymium filter is the way to go. Additionally, you might find a pair of polarising filters useful so that you can fine tune the brightness to your desired level. 

8 hours ago, Sator Steve said:

Hi there,  I am looking at the moon right now and there's a planet or star to the right of it as of 2245 in Long Melford, Suffolk, England. Any ideas on what it could be? I don't have any good programs to work it out, so if you have any recommendations for a program (Windows, apk) that's useful, that'd be helpful too, thanks muchly!

On Windows, I suggest Stellarium

How did you get on with using binoviewers and can you reach focus with them in your current scopes? If it was me I would always look to binoview for planetary unless it was impossible or for a lightweight travel setup where weight is important. 

1 hour ago, newbie alert said:

Have I missed something as I thought imaging/ viewing the sun you're looking at 1 wavelength so a simple achromat is just as good as a triplet or a quad or whatever..  a lunt is a achromat for a example..

A Hershel Wedge is for white light solar, so all the wavelengths are transmitted and an ED/APO scope is preferable. For HA you are correct.

Can you get to the terminals with a multimeter when the batteries are installed? If so you can check the voltages at different points to find where the contact is not connecting properly.

Alternatively, how about buying a 12V LiPo battery (or several) and powering through the working power socket? Over time a rechargeable 12V battery is going to be more cost effective than continually buying new AAs.

A focal length of 1250mm is almost the same as a 6-10" dob (1200) and I am sure there are many people that are happily using those solely with 1.25" eyepieces. There are a few targets that will be very tight in terms of the field of view but most things will fit in. Finding things is going to be the hardest part, a 9x50 RACI finder will help, but this is quite large compared to the telescope. The focal length is also roughly double that of your telescope so you can simulate the maximum field of view by using your longest focal length eyepiece and a 2x barlow. Perhaps try leaving the barlow in for an entire session and see how you both get on with it, just remember that the 90mm Mak will gather less light so stars will be dimmer in it (and some dim ones you see in the 130 won't appear in the 90).

2 hours ago, Ben the Ignorant said:

The 130/900 Sky-Watcher I got from Teleskop Service IS parabolic

Interesting, I guess I was wrong then. It is good news that these scopes are being supplied with parabolic mirrors. 

2 hours ago, awlfc said:

First night out with my score last night. Decent breaks in the clouds and with the 10mm eyepiece that come with the scope I could see and find everything I pointed it at. But when i put my BST lenses in all i could see was my eye lashes. What am I doing wrong and why is the twist thing on the BST an extra focuser 

The twist up eyecup is to help get your eye the correct distance from the lens. Set it up if you don't wear glasses, down if you do. 

1 minute ago, vlaiv said:

 

Bottom line - I have no idea if it is indeed spherical or parabolic. Simple star test would show? Missing coma, and apparent spherical aberration in defocused star image ...

 

From a quick Google it looks like Synta might actually be the only manufacturer making 130/900 Newtonians so perhaps testing would be easier than I first thought. I'm not sure how much coma should be visible at f7 though. 

2 hours ago, Geoff Barnes said:

I like the answers and information you give to all queries on the forum Ricochet, they are always on point, clearly explained and helpful. 

Thanks, Geoff. 

1 hour ago, vlaiv said:

This is a claim that I came across more than few times. I had the said scope, and I'm not 100% convinced that this is true. While at the time I did not have enough knowledge to know the difference, and looking back at my observations at the time, I would say, yes, probably that scope did have spherical mirror, since I had so much better planetary views with other scopes after that one.

You are right, as without someone testing of all the telescopes or manufacturers stating the mirror is spherical we cannot know for sure, but only infer from "parabolic primary" being missing from the advertising (and for synta products, the name).

On 14/06/2019 at 10:23, wesdon1 said:

Hi all! Just a question from a newbie. Do expensive eyepieces tease out more contrast/detail on planets when using my 130/900 Newtonian reflector? I've seen some gorgeous views of my ( so far ) favourite planet Jupiter ( because it's the easiest to find and veiw lol ). But it's never quite crisp and contrasted enough? I'm very aware of bad seeing, but i recall a brilliant seeing night a while back, and still Jupiter was not very large and the cloud bands not very well defined? I've collimated my mirrors, but i'm assuming all other things being ok, it could be my cheap SkyWatcher 10, 25mm eyepieces and my cheap 3.6mm Plossl eyepiece ( the plossl cost me £17 ) that are to blame? I just can't stop thinking i would likely see Jupiter as a much larger and clearer image if i bought some super expensive eyepieces? Or should i just invest that money on a larger aperture reflector telescope instead? Considering for same money i spend on said EP's ( £400-500 ) i could buy a huge light bucket on a Dob mount ? Thank you in advance for any advice you can give me.

Better quality eyepieces do give better views but more expensive eyepieces are not necessarily better quality. Baader Classic Orthos, for example, give high quality views at the expense of field of view and eye relief whilst still being at the cheaper end of the market. Double the price and you can buy Vixen SLVs which add decent eye relief to high quality views or you can buy Baader Hyperions which give decent eye relief and wider views at the expense of image quality.

Moving on to your current situation, the biggest issue you will have at the moment is how low Jupiter is in the sky. In future years when it is higher, you will get better views with the same equipment.

The second issue is that I believe all of the 130/900 Newtonians on the market have spherical mirrors, which will limit their sharpness. I think that a 3.6mm eyepiece will be producing a magnification beyond the capabilities of this telescope regardless of whether it is good or not. The 10mm supplied with these telescopes (assuming Synta 10mm MA) is usually regarded as not being a great performer and could be replaced with a better eyepiece, however, I would not invest too much into eyepieces for this scope. It is probably better to buy eyepieces suited for your next telescope instead.

On 10/06/2019 at 20:34, Gabe said:

Hey, I wanted to say thanks too all the people who have helped so far. I would also like to thank michael8554 for telling me that the THING is called a diagonal 😆 

 

I was wondering, if I got a Barlow lens, would that help my problem? 

Now that you know to always use the diagonal in the focuser, I don't think you really have a problem as it seems that your eyepieces reach focus. If you're wanting to use the telescope without the diagonal then you will need an extension tube rather than a barlow.  I think the light path of a 1.25" diagonal is usually around the 65-70mm mark so you will need an extension tube of this sort of length to replace the diagonal. 

If you want more magnification then the 10mm and 2x barlow is probably going to be too high for your telescope. An 8 or 9mm eyepiece might be the limit.

On 09/06/2019 at 16:58, Pollyanna24 said:

Backing the focus know all the way to infinity (I'm too scared to go all the way back for fear the knob will come all the way off) does not help and makes the ring of light bigger. 

Turn the focuser knob one way until it will not turn any more. Now turn it the other way and count how many turns it takes for you to reach the point where you reach the point where the knob will not turn. With a 6SE (I assume this is your scope)  this should be in the region of 30 turns. If you have about 30 turns then you have the full range of travel, if you have fewer then there is some internal issue that needs repairing.

If you have the full range of the focuser then try aiming it at terrestrial targets at varying distances and see if any of them are in focus. Once you find something that is in focus you can try targets farther away and see if you can bring them all to focus. If you can focus on something very far in the distance then you should be quite close to the focus point for astronomical targets and can try again at night.

6 hours ago, Arran townsend said:

The transmission graph looks almost identical to the skytech cls clip filter

They might be the same filter. SVBony don't make anything, they just order items in large enough quantities to get their name printed on them. Skytech could be the same, or even the own brand name that the manufacturer has been selling them under. 

With regards to filters, I think this is an area where it is worth paying for a premium brand. If you've got LED lighting in the area then it is probably worth your while looking at the new(ish) IDAS filter that is designed with that in mind.