Posts Made By: dan hilts

Wonder what it does for the running time when using battery power?

I get 90 minutes on my laptop. (only 17 with the gloves and beer fridge plugged in.)

dan

<< I still think I haven't seen a good photo of NGC1023, so if anyone can provide me a link I'll be very grateful. >>

Try this one:

http://aida.astroinfo.org/displayimage.php?album=8&pos=277

Look for file 278/383. Click on the image for the high res version.

regards,
dan

http://www.astromart.com/forums/viewpost.asp?forum_post_id=621286&poll_id=&news_id=&page=

dan

With a 1.25" focuser, the absolute maximum field size will be 27-28mm diameter.

You can field this image with a 32mm plossl and there are a good number of those to choose from today. The Orion or GSO plossls would do quite nicely.

However, a 27mm image is not going to show the whole of the Pleiades. Maximum field will be somewhere around 1.25 degrees. The Pleiades are rated at almost 2 degrees. M31 is the only Messier object that is larger. Still a 32mm plossl is a good fit in a scope this size and it provides good eye comfort. I think the added field over the 25mm Plossl is worth the price.

have fun,
dan

Hi Paulo,

I saw your post when you first placed it but I was hesitant to reply for one reason: safety is always an issue when using telescopes to view solar light. I would feel truly horrid if someone was injured because they followed sugestions I made. I would also feel bad if I didn't speak up when I could have prevented an injury. Hopefully others will comment.

Personally, I would not place the Barlow in front of the wedge.
Cemented optics do not fare well in the light path of a solar image. This includes Barlows, eyepieces, filters etc. The cement in these optics can heat up to dangerous levels and fracture the lenses. Even if the glass does not break, the lens is ruined because the cement bond is destroyed by the heat. Additionally, a Barlow lens is placed very close to the image plane so the image will be very intense at that position. If the image gets slightly out of the field of view, the full heat of the sun is going to be shining on the edge of the lens and the lens housing. Like frying bugs with a magnifying glass, it is not something I would want my optics to endure.

Lastly, all lenses have some absorption of the light passing through. Some glasses have more absorption than others. An unfiltered solar image is very intense and even 1% absorption is going to cause a lot of heat to build up.

Solar projection used to be very popular and many telescope kits were equipped with a solar projection screen. However, this was in the time when scopes were equipped with simple eyepieces such as the Ramsden and Hyguens designs which use no cemented elements. If your Barlow uses airspaced lenses,(see ad #595319), you may be able to use it ahead of the wedge, but for the reasons I have stated, I wouldn't do it.

Have fun but play safe,

dan

I see the registrars are planing on sending out tickets starting today.

http://www.scas.org/wsp_alerts.html

dan

I got a glimpse of the two planets on Saturday but the a major storm rolled in through Toronto region and we are under some heavy cloud cover so I missed the the moon.

Yes, it looks like Santa. Thanks for sharing.

dan

The Celestron is the as the Baader. Response curve is attached.

I have one of these and it has worked well for my visual observing. I don't do photgraphy.

dan

Original packaging for a large item can add value. I recently sold a pair of 20 X 100 binos that still had the factory shipping materials. The fellow who purchased them was very excited because the binos were still just like "new". I think the boxes closed the deal. There was value there for me.

It could be perceived that a fellow who cares enough about his stuff to keep the original boxes in good condition, probably cared for the items in the same way. That has value even if it is not reality.

Having the boxes also suggests that the item may have been recently purchased, especially if the boxes are bulky. It also suggests that the seller is the original owner. The buyer has to ask the right questions to get the right information.

Some buyers who turn over a lot of equipment like the boxes for the reasons stated above. Equipment can be easier for them to resell. That has value.

Now I still have the original boxes for my RKE eyepieces I purchased in the early 80's although they are well scuffed from years of handling. I don't think they add any value to the eyepieces.

dan

Keith,

Eyepiece projection always requires that the eyepiece be moved outwards from the position of focus for visual observation. Just how far out depends on a couple of factors but it will never be more than the focal length of the eyepiece used. For example, a 25mm eyepiece used for projection will never require more than 25mm of out focus.

There are formulas but because eyepieces are typically not simple lenses, it is difficult to tell exactly where to measure from. However, you can get a very good idea of the mechanical setup required by projecting the image of the moon, (or a distant street light), onto a card held up to the eyepiece. Hold the card about three inches back and adjust the focus for best projected image.

Eyepiece projection results in an magnified image. The distance to the image is determined by the magnification and the focal length of the eyepiece used for projection. M = (distance to image - focal length)/ focal length. A special case occurs when the primary image is exactly two focal lengths from the lens since this puts the projected image at exactly the same distance and magnification = 1. I have attempted to illustrate this in the simple sketch attached.

have fun!

dan